ERDC/CHL TR-20-15 

Regional Sediment Management (RSM) Program

Sediment Sorting by Hopper Dredging and 

Pump-Out Operations: Sampling Methods and 

Analysis 

Coastal and Hydraulics Laboratory 

Duncan B. Bryant, Anthony M. Priestas, S. Jarrell Smith, and 

Katherine E. Brutsché

August 2020

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Regional Sediment Management (RSM) Program ERDC/CHL TR-20-15 

August 2020 

Sediment Sorting by Hopper Dredging and 

Pump-Out Operations: Sampling Methods and 

Analysis 

Duncan B. Bryant, Anthony M. Priestas, S. Jarrell Smith, and Katherine E. Brutsché 

Coastal and Hydraulics Laboratory

US Army Engineer Research and Development Center

3909 Halls Ferry Road

Vicksburg, MS 39180-6199

Final report

Approved for public release; distribution is unlimited

Prepared for US Army Corps of Engineers, Headquarters

Washington, DC 20314-1000

US Department of the Interior, Bureau of Ocean Energy Management

Washington, DC 20240

US Army Corps of Engineers, Jacksonville District

Jacksonville, FL 32207-8175

Under Program Element No. 110; Project Number 484149; Task No. A1040;

Funding Acct Code U4371904; AMSCO Code 008303
ERDC/CHL TR-20-15 ii

Abstract

Hopper dredging operations for beach and nearshore placement typically 

include periods of overflow, which produces some degree of separation 

between the size fractions of the dredged sediment. The degree of 

separation and the controlling factors are presently poorly known. This 

report focuses on laboratory experiments aimed at determining (1) 

suitable sampling methods on a dredge, (2) composite sampling 

techniques to reduce analysis cost, (3) associated sampling intervals to 

achieve suitable sediment representation of a hopper load, and (4) a 

hydraulic means of sample splitting. Results showed that no statistical 

difference exists among the three methods used to sample the hopper weir 

overflow. The method used to sample deposited hopper sediment 

identified a bias in the percent fines that resulted from flow sheltering. 

Further, it was found that composited samples were able to quantify the 

concentration and percent fines accurately, although an analytical data 

experiment showed that the accuracy of a composited sample is dependent 

on the sampling intervals. The accuracy of the fines and concentration 

from a hydraulic sample splitter was found to be dependent on median 

grain size, with fine sediment being evenly distributed and coarser 

sediment increasing the error in concentration and grain size distribution.

DISCLAIMER: The contents of this report are not to be used for advertising, publication, or promotional purposes. 

Citation of trade names does not constitute an official endorsement or approval of the use of such commercial products. 

All product names and trademarks cited are the property of their respective owners. The findings of this report are not to 

be construed as an official Department of the Army position unless so designated by other authorized documents.

DESTROY THIS REPORT WHEN NO LONGER NEEDED. DO NOT RETURN IT TO THE ORIGINATOR.
ERDC/CHL TR-20-15 iii

Contents

Abstract.................................................................................................................................... ii

Figures and Tables...................................................................................................................v

Preface....................................................................................................................................vii

1 Introduction ...................................................................................................................... 1

1.1 Background........................................................................................................1

1.2 Motivation ..........................................................................................................2

1.3 Objectives...........................................................................................................4

1.4 Approach ............................................................................................................4

1.5 Document organization.....................................................................................4

2 Methods ............................................................................................................................ 6

2.1 Materials ............................................................................................................6

2.2 Overflow experiments........................................................................................7

2.2.1 Weir overflow............................................................................................................... 8

2.2.2 Sampling methods ....................................................................................................12

2.2.3 Dredge hopper ..........................................................................................................14

2.3 Hydraulic splitting of sediment-water mixtures .............................................21

2.3.1 Recirculating tank system ........................................................................................21

2.3.2 Sediment mixtures and schedule ............................................................................22

2.3.3 Splitting procedure....................................................................................................23

2.3.4 Analysis methods ......................................................................................................24

2.4 Composite sampling of hopper inflow............................................................24

2.4.1 Data source ............................................................................................................... 24

2.4.2 Analysis methodology ...............................................................................................25

3 Results.............................................................................................................................28

3.1 Physical sampling ........................................................................................... 28

3.1.1 Weir overflow results.................................................................................................28

3.1.2 Hopper sampling.......................................................................................................32

3.1.3 Hopper sampling via plate sampler.........................................................................33

3.2 Hydraulic sample splitting.............................................................................. 34

3.2.1 Sediment composition..............................................................................................34

3.2.2 Sediment concentration ...........................................................................................35

3.3 Numerical experiments ...................................................................................37

4 Discussion and Conclusions.........................................................................................39

4.1 Sample compositing....................................................................................... 39

4.2 Sample splitting.............................................................................................. 40

4.3 Sampling methods...........................................................................................41

4.3.1 Hopper overflow weir sampling................................................................................41

4.3.2 Hopper sediment bed sampling ...............................................................................42
ERDC/CHL TR-20-15 iv

4.3.3 Hopper inflow sampling............................................................................................43

4.4 Conclusions..................................................................................................... 44

References.............................................................................................................................46

Unit Conversion Factors.......................................................................................................47

Acronyms and Abbreviations...............................................................................................48

Report Documentation Page
ERDC/CHL TR-20-15 v

Figures and Tables

Figures

Figure 1. Gradation of the VS, FS, and CS. .............................................................................. 7

Figure 2. Weir overflow schematic............................................................................................ 8

Figure 3. Sediment mixing tank................................................................................................ 9

Figure 4. Schematic of weir tank. Tank dimensions are shown with design depths 

of sand, water, and design freeboard. Not to scale. .............................................................10

Figure 5. Photograph of weir overflow laboratory setup. Laboratory setup 

indicates supply tank, weir tank, and receiving tank. Blue line indicates the path 

of flow from the supply tank to the receiving tank................................................................11

Figure 6. Model weir tank in overflow.....................................................................................13

Figure 7. Three weir overflow sampling devices: (a) bottle, (b) box, and (c) tube...............14

Figure 8. Schematic cross-sectional view of the weir tank with bed samplers. 

Samples were taken during the overflow period as the bed developed and raised, 

which filled the sampler. A core was taken adjacently once the surface water 

had drained...............................................................................................................................16

Figure 9. Plan view of the plate sampling device. The fully constructed version 

with chain bridling is shown on the left..................................................................................16

Figure 10. Generalized operational aspects of the plate sampler. Rest position 

(A), under load upon retrieval (B), and sample recovery position (C and D)....................... 17

Figure 11. Deployment (left) and retrieval (right) of the plate sampler in the model 

hopper tank...............................................................................................................................18

Figure 12. Image sequence showing the sample recovery process. (1) The 

sample was retrieved, and (2) the inner disk was allowed to rest on a riser that 

exposed the sediment collected on its surface. (3) A short core was inserted to 

refusal (4), and sediment above and around the short core was cleared away (5

and 6). The sample was then slid off the disk into a container and then 

composited (7 and 8)...............................................................................................................18

Figure 13. Schematic diagram of the plate sampler experiment design............................19

Figure 14. Recovered core used to compare against composited bed samples...............20

Figure 15. Recirculating tank schematic for hydraulic sample splitting. ............................22

Figure 16. Recorded starboard velocity and specific gravity for hopper load 93...............25

Figure 17. Example of subset sampling Load 93. A fixed sampling interval with no 

phase shift (Subset 1) and a phase shift of 10 (Subset 2)..................................................26

Figure 18. Example of two subset samplings of load 93. Two random sampling 

realizations with average sampling interval of 156 s. Note that the samples are 

pulled randomly, not at a fixed sampling interval.................................................................. 27

Figure 19. Results of weir sampling tests, average percent fines between weir 

overflow samples and receiving tank samples. Sampling method only refers to 

the overflow weir.......................................................................................................................29

Figure 20. Average concentration for the different methods of weir overflow 

sampling and receiving tank. ..................................................................................................30
ERDC/CHL TR-20-15 vi

Figure 21. Mean concentration for all sampling methods for weir overflow and 

receiving tank samples............................................................................................................31

Figure 22. Variability of concentration for each weir overflow sampling method.............. 31

Figure 23. Comparison of the percentage fines retained in the hopper tank 

collected by the pipe sampler and a core for two test cases...............................................33

Figure 24. Results comparing the percentage fines captured using the plate 

sampler and a 2 in. diameter coring device. .........................................................................33

Figure 25. Sediment concentrations averaged by test. Error bars represent the 

SEM. T = tank port, R = return line port, F = fine sand, and C = construction sand. 

Dashed line shows the known system concentration. .........................................................35

Figure 26. Sediment concentrations averaged by sampling port and sediment 

type. Error bars represent the averaged SEM. Dashed line shows the known 

system concentration...............................................................................................................36

Figure 27. Averaged concentrations of mud (dashed pattern) and sand (dotted 

pattern) for each test grouped by initial mud content (10%, 20%, 30%). T = tank 

port, R = return line port, C = construction sand, and F = fine sand. For 

comparison, the expected concentrations of sand and mud are also plotted (E10, 

E20, E30). ................................................................................................................................. 37

Figure 28. Results of numerical experiment of inflow sampling interval, showing 

the mean absolute error and the 95% interval percent error for both the fixed and 

random interval sampling........................................................................................................38

Tables

Table 1. Overflow testing procedure.......................................................................................12

Table 2. Test matrix for weir overflow sampling.....................................................................13

Table 3. Sample splitting test matrix. .....................................................................................23

Table 4. Summary table of sediment concentrations for each experiment. 

Experiment IDs annotated with R refer to receiving tank samples while those with 

W refer to weir tank samples. Std Dev refers to standard deviation, and Std Error 

refers to the standard error of the mean. ..............................................................................30

Table 5. Summary table comparing the relative RE in concentrations 

between the weir samples and the mean value in the receiving tank for all 

sediment mixtures and sampling devices.........................................................................32

Table 6. Averaged sediment characteristics of samples collected from the midtank port (T) and the return line port (R). Initial mud/sand ratios represent the 

starting sediment mixture for a given test followed by ratios after sampling. IDs 

appended with C refer to construction sand tests and with F refer to fine sand 

tests. ..........................................................................................................................................34
ERDC/CHL TR-20-15 vii

Preface

This study was conducted for the Regional Sediment Management (RSM)

Program through an Interagency Agreement (IAA, number M16PG00023) 

between the US Department of the Interior, Bureau of Ocean Energy 

Management (BOEM); the US Army Corps of Engineers (USACE), 

Jacksonville District (SAJ); and the US Army Engineer Research and 

Development Center (ERDC), Coastal and Hydraulics Laboratory (CHL), 

RSM Program under Program Element No. 110; Project Number 484149; 

Task No. A1040; Funding Acct Code U4371904; AMSCO Code 008303.

Funding was provided by BOEM and the USACE ERDC RSM Program.

Dr. Clay McCoy was the Technical Lead and Project Manager from SAJ, 

Mr. Doug Piatkowski was the Contracting Officer’s Representative for 

BOEM, and Ms. Leighann Brandt was the Technical Lead from BOEM.

The work was performed by the Field Data Collection and Analysis Branch 

and the Coastal Engineering Branch of the ERDC-CHL Navigation 

Division, and the Coastal Processes Branch of the ERDC-CHL Flood and 

Storm Protection Division. At the time of publication of this technical 

report, Mr. William C. Butler was Chief of the Field Data Collection and 

Analysis Branch, Ms. Lauren M. Dunkin was Chief of the Coastal 

Engineering Branch, and Ms. Ashley E. Frey was Chief of the Coastal 

Processes Branch. Dr. Jacqueline S. Pettway was Chief of the Navigation 

Division, and Dr. Cary A. Talbot was Chief of the Storm Protection 

Division. Dr. Katherine E. Brutsché was the National RSM Program 

Manager, and Mr. Charles E. Wiggins was the ERDC Technical Director 

for Navigation. The Director of ERDC-CHL was Dr. Ty V. Wamsley, and 

the Deputy Director of ERDC-CHL was Mr. Jeffrey R. Eckstein. 

Support for the development and implementation of the IAA was provided 

by Ms. Jackie Keiser, Mr. Jason Engle, and Dr. Kelly Legault of the RSM 

Regional Center of Expertise. The USACE administrative point of contact 

was Ms. Liz Fiocchi. Mr. Douglas Piatowski, Ms. Leighann Brandt, and 

Mr. Paul Knorr (BOEM), Dr. Michael Miner (The Water Institute of the 

Gulf), and Dr. Clay McCoy (SAJ, RSM Regional Center of Expertise) are 

thanked for the development of the study concept and their valuable input 

toward the study plan and methods.

COL Teresa A. Schlosser was the Commander of ERDC, and the Director 

of ERDC was Dr. David W. Pittman.
ERDC/CHL TR-20-15 1

1 Introduction

1.1 Background

In shore protection, ecosystem restoration, and navigation projects where 

sediment is placed on the beach or in the nearshore, coastal project 

managers are required to ensure that sediment taken from source areas 

(e.g., offshore borrow site, navigation channel, inlet complex) is 

compatible with the sediment characteristics at the placement site (e.g., 

the beach or nearshore). Important factors to consider are sediment grain 

size, composition, sorting, and color (Dean 2003). Additionally, some state 

regulations across the nation (such as Florida’s “Sand Rule”) specify 

allowable thresholds of percent fine sediment relative to sand content 

(Florida Department of Environmental Protection 2017; FL 

Administration Code r. 62B-41.007(2)(j)). The definition of fine sediment 

may differ from state to state; however, it is generally recognized as either 

the sediment passing the no. 200 (75 μm)* sieve in accordance with the 

Unified Soil Classification System or the material passing the no. 230 

(63 μm) sieve in accordance with the Udden-Wentworth scale. The latter 

classification was used in this study. 

When determining compatibility between the source sediment and the 

native sediment, it is typically assumed that textural properties (e.g., 

sorting, mean grain size, and percent sand) are unchanged from the in situ 

borrow area through dredging and conveyance to the placement site.

However, it is generally recognized that hopper dredges implementing 

overflow (the intentional discharge of supernatant water) coarsen their 

load respective to the source material through preferential loss of fines 

suspended in overflow (the gain in hopper load through this process is 

known as economic loading). Additional loss of fines may occur at the 

draghead and during pump-out beach placement operations. Presently, 

regulations do not consider any possible reduction in fine sediment 

through the dredging process when assessing sediment compatibility. 

 

* For a full list of the spelled-out forms of the units of measure used in this document, please refer to US 

Government Publishing Office Style Manual, 31st ed. (Washington, DC: US Government Publishing 

Office 2016), 248-52, https://www.govinfo.gov/content/pkg/GPO-STYLEMANUAL-2016/pdf/GPOSTYLEMANUAL-2016.pdf.
ERDC/CHL TR-20-15 2

It is hypothesized that, based on this coarsening process, dredged material 

containing a higher concentration of fines than currently permitted by law 

could be used in coastal flood risk management, ecosystem restoration, 

and navigation projects, potentially saving money on the project by 

making use of previously undesirable sediment resources. Thus, the 

volume and availability of offshore sediment deemed compatible for 

coastal restoration projects to support resiliency of both coastal 

infrastructure and habitat could be increased. Understanding and 

quantifying the loss of fines through the dredging process would allow 

coastal managers to better estimate the compatibility of dredged material 

for beneficial use projects.

The potential loss of fines through dredging was first observed from 

geotechnical investigations of the Florida Sediment Assessment and Needs 

Determination (SAND) study (Ousley et al. 2014) and later quantified by 

Coor and Ousley*. Here, the authors attempted to quantify the total loss of 

fines by examining the sediment compatibility data of borrow and post-fill 

sediment sources for multiple dredging and shore protection projects. In 

essence, this involved examining the composite grain size statistics 

recorded at the borrow sites and beaches. From this it was discovered that 

the mean reduction in fines was approximately 75% (range <63 μm: 

0.86%—25%). In one instance, the fines content was reportedly reduced 

from 25% at the borrow site (Tampa Harbor Entrance Channel) to 2.5% at 

the placement site. However, the percent fines recorded at the other 

borrow sites were very low (3% or less), and therefore it is not well 

understood if the same magnitude of fine sediment losses should be 

expected from borrow sites with a much greater fines content (e.g., 20%). 

Additionally, where in the dredging and placement process fine sediment 

loss occurred could only be speculated. Therefore, this present study is 

meant to fill in some of the gaps to predict fine sediment losses through 

dredging and placement activities.

1.2 Motivation 

To quantify the loss of fines through the dredging and placement process, 

information on the sediment characteristics needs to be determined at 

various locations including (1) the borrow site, (2) the dredge, and (3) the 

 

* Coor, J. L., and J. D. Ousley. (Forthcoming). Historical Analysis of Fines Lost during Beach Nourishment. 

ERDC-CHL Technical Note. Vicksburg, MS: US Army Engineer Research and Development Center.
ERDC/CHL TR-20-15 3

nourishment site. Each of these locations creates challenging sampling 

and analysis scenarios, but none more so than the dredge itself. The 

hopper capacity of trailing suction hopper dredges (TSHDs) can vary on 

the order of a few thousand to tens of thousands of cubic yards. Germane 

to this study is being able to sample incoming dredged material in a way 

that the average value (of some observation) of the population is well 

represented by the average value determined from a subset of independent 

samples. To do this requires taking numerous samples throughout the 

loading cycle due to the fact that (1) sample volumes are very small relative 

to the total hopper load and (2) the mass flux and/or sediment 

composition coming into the hopper can vary greatly in time. However, 

the costs of analyzing so many samples is prohibitive. Instead, the average 

value could be determined by means of compositing, provided that the 

errors in compositing samples are acceptably small. 

Compositing is a type of physical averaging where multiple independent 

samples of some process are combined into a single sample. In this way, a 

single measurement from the composited sample should represent the 

arithmetically derived average of the individual samples. A primary 

concern in this approach is unintended bias associated with covarying 

parameters, such as slurry concentration and slurry flowrate. If the 

covariance is negative and strong, the arithmetic mean of a single sampled 

parameter (such as concentration) will deviate from the true average as 

estimated from the first moment of the covarying quantities. Another 

important consideration is that a subsample (or aliquot) of a composited 

sample must be obtained in a way that is representative of the composite, 

which is possible only through homogenization. As many tens of kilograms 

of sediment per hopper load are expected, a procedure needed to be 

developed to homogenize and subsample sediments from the hopper and 

the inflow. Splitting sediments collected from the inflow is more 

complicated if the average concentration is also desired, given that this 

material is in the form of a slurry. 

Another consideration is the sampling interval. Errors are introduced 

when sampling intervals are too coarsely spaced. Thus, it is necessary to 

know the minimum number of samples required such that a composited 

sample sufficiently represents the population and the sort of error that 

might be expected as a function of sample number. Part of this study 

attempts to answer these questions specific to the study needs.
ERDC/CHL TR-20-15 4

In summary, the motivation for this study was to develop and test 

sampling methodologies and analysis schemes within a laboratory setting, 

and to develop methods for homogenizing and subsampling composited 

samples. This will help to guide the sampling schemes to be conducted in 

the field and allow for robust sediment characterization needed to quantify 

the loss of fines through the dredging and placement process.

1.3 Objectives

Specifically, the objectives of this study were (1) to determine suitable 

sampling methods for collecting samples at the dredge, (2) to determine 

whether samples can be composited into a smaller subset of samples, (3) 

to test a hydraulic means of subsampling large-volume, composited 

samples, and (4) to determine the appropriate sampling interval required 

to obtain the minimum number of samples needed to meet a designated 

error threshold. 

1.4 Approach

To achieve Objective 1, a laboratory experiment was designed to simulate 

the process of hopper filling and subsequent overflow to test different weir 

sampling methods, as well as methods to sample the hopper directly. The 

same experiment was used for Objective 2 by comparing composited 

samples from the overflow to individual samples. For Objective 3, an 

experiment was designed using a recirculating tank to withdraw aliquots 

from a known concentration. For Objective 4, a numerical experiment was 

designed using readily available Dredging Quality Management (DQM) 

data to determine the potential error associated with sampling frequency. 

The achievement of each of these objectives is further explained in 

Chapter 2 Methods of this report.

1.5 Document organization

Chapter 2 of this report discusses the various methods used in this study, 

including physical sampling and sample analysis. Physical sampling 

includes sampling of the model weir tank and hopper. A discussion on how 

the weir tank was constructed and the set up of the entire experiment is 

included. Sampling (i.e., box, bottle, and tube samplers) and sediment 

analysis methods for the weir tank experiment and hopper are also 

discussed. Chapter 2 also includes a discussion of sample analysis methods 

including a sample splitter experiment and a numerical experiment using 
ERDC/CHL TR-20-15 5

DQM data to determine the sampling frequency required to obtain 

acceptable sampling error from the dredging process. Chapter 3 presents 

results from the overflow weir, hopper sampling, sample splitting, and 

numerical experiment for determining sample frequency. A discussion and 

conclusions of these results are provided in Chapter 4.
ERDC/CHL TR-20-15 6

2 Methods

This chapter details the materials, design, and procedures used to test the 

physical sampling and sample analysis methods. The first section provides 

details on the sediments used in this study, followed by a section 

describing the laboratory hopper overflow and subsequent sampling 

methods. The final sections detail the hydraulic sample splitter tested for 

sample analysis and an analytical experiment to determine the error 

introduced by the sampling frequency. 

2.1 Materials

Three sources of sediment were used for the laboratory testing. To 

determine the grain size distribution, samples were analyzed using a 

Malvern laser scattering instrument. The first sediment was a local 

sourced loess referred to as Vicksburg silt (VS). The gradation of the VS is 

given in Figure 1 with a measured d50 = 22.6 μm, a d10 = 7.4 μm, and a d90

= 48.6 μm. The second sediment used was a fine sand (FS) with a d50 = 

186.3 μm, d10 = 117 μm, and a d90 = 295 μm. The gradation for the FS is 

given in Figure 1. A sand used commonly in mortar mix, referred to 

throughout this document as construction sand (CS), was also used in the 

laboratory testing. This uniform sand was found to have a d50 = 408 μm, a 

d10 = 264 μm, and a d90 = 626μm. The grain size distribution for this sand 

is provided in Figure 1. 
ERDC/CHL TR-20-15 7

Figure 1. Gradation of the VS, FS, and CS. 

2.2 Overflow experiments

This section describes the laboratory setup and procedures used for 

sampling the overflow of a model hopper. The overflow experiments were 

designed to test different sampling methods and the effectiveness of 

sample compositing. These experiments were not designed to mimic the 

flow and sediment dynamics within a prototype hopper. Instead, the only 

necessary design criteria included scaling the flow rate over the weir and 

matching the vertical loading rate of the sediment bed, considered in the 

hopper load parameter, H*, as defined by van Rhee (2001) in 

Equation 2-1. The numerator, v0, is the vertical loading rate calculated by 

dividing the hopper flow rate by the hopper area. The denominator, ws is 

the hindered settling velocity based on the sediment concentration as 

defined by Richardson and Zaki (1954) in Equation 2-2. Here, w0 is the 

single grain settling velocity, C is the concentration, and n is an empirical 

coefficient dependent on grain size.

HH∗ = vv00

wwss

(2-1)

wwss = ww0(1 − CC)nn (2-2)
ERDC/CHL TR-20-15 8

The experiments conducted in the laboratory were meant to represent a 

generic dredging event; thus, a typical concentration value of 15% (by 

volume) was chosen, which corresponds to 400 g/L by mass. This is a 

reasonable value for inflow concentration, which can vary from 10% to 

30% but low enough to pump as a slurry without using special equipment.

2.2.1 Weir overflow

To test the sampling and compositing hypothesis, a model hopper dredge 

was designed. To build this in a laboratory, three tanks were needed: (1) a 

supply tank, (2) a weir tank, and (3) a receiving tank. The supply tank 

holds the sediment mixture and represents the hopper inflow. The weir 

tank represents the prototype hopper and includes an overflow weir. The 

receiving tank contains all the contents collected from the overflow and is 

representative of the outflow from the hopper. Figure 2 provides a 

schematic of the tanks, valves, instruments, and pumps needed to execute 

the model hopper dredge.

Figure 2. Weir overflow schematic. 

The stainless steel supply tank had a maximum volume of 1,540 L. The 

bottom of the cylindrical supply tank was beveled and fed into a 10 cm 

(4 in.) nominal pipe connected to a Honda WT40 gas-powered trash pump 

capable of handling solids up to 2.54 cm in diameter (Figure 3) and had a 

maximum flowrate of 28.4 L/s (450 gal/min). To maintain sediments in 

suspension, the tank also had two mixing paddles located at the tank 

bottom and mid-depth driven by an electric motor at 120 rpm. A set of ball 

valves was used to recirculate the mixture from the pump to the supply 

tank and for transferring to the weir tank. The flow rate of the transferred 

material was monitored using an in-line Endress+Hauser Proline Promag 

50 electromagnetic flowmeter.
ERDC/CHL TR-20-15 9

Figure 3. Sediment mixing tank. 

Figure 4 provides a schematic of the designed depth of settled sand, 

maximum water depth, and freeboard distance. The basin was 88.4 cm 

deep with an area of 62.8 cm × 152.4 cm. The overflow weir was 53.9 cm 

from the basin floor with an opening width of 10.16 cm. A target inflow 

rate of 4.7 L/s was determined to achieve the desired sediment loading 

rate of 5 mm/s, which was controlled using a gate value immediately 

upstream of the weir tank. The design volume of sand collected in the tank 

was 384 L, which equates to bed height of 41.2 cm assuming a uniform 

distribution with a bulk density of 1,600 kg/m3. The expected bed height 

was used to determine the maximum water depth over the weir. The flow 

rate and exit velocity of the overflow was calculated using the sharp 

crested weir equation (with a Cd = 0.6), which was designed to be similar 

to that encountered in dredge plants. 
ERDC/CHL TR-20-15 10

Figure 4. Schematic of weir tank. Tank dimensions 

are shown with design depths of sand, water, and 

design freeboard. Not to scale. 

The overflow discharged from the weir was captured in a separate 

aluminum basin. At the end of the loading cycle, the material was then 

transferred to the receiving tank using a nominal 5 cm (2 in.) sump pump. 

Special attention was taken during testing to move all the overflow 

material to the receiving tank. The receiving tank was identical to the 

supply tank except a nominal 5 cm (2 in.) gas-powered semi-trash pump 

was used to recirculate the contents of the tank. The maximum flowrate of 

the receiving tank pump was approximately 15.8 L/s (250 gpm). A 

photograph of the laboratory setup with the process moving from right to 

left following the blue line is shown in Figure 5.
ERDC/CHL TR-20-15 11

Figure 5. Photograph of weir overflow laboratory setup. Laboratory setup indicates 

supply tank, weir tank, and receiving tank. Blue line indicates the path of flow from 

the supply tank to the receiving tank. 

The sediments used for the experiment consisted of three constant volume 

mixtures created with increasing fines content of 10%, 20%, and 30%. 

Each mixture was created in triplicate for repeatability and statistical 

significance. To achieve the 10% fines mixture, 526 kg of CS and 59 kg of 

VS were combined with 1,241 L of water. Respectively for the 20% and 

30% fines mixtures, the masses were 468 kg CS + 117 kg VS + 1,241 L 

water, and 409 kg CS + 175 kg VS + 1,241 L water. All sediment masses 

used in the mixture calculations were corrected for moisture content prior 

to mixing. The testing procedure is provided in Table 1. 
ERDC/CHL TR-20-15 12

Table 1. Overflow testing procedure. 

1 Check plumbing.

2 Identify pre-measured sediment bags for test.

3 Prepare sampling bottles and sampling method/equipment.

4 Check that flowmeter/scale are logging.

5 Fill tank 1 with desired amount of water.

6 Turn on recirculation pump and paddles for supply tank.

7 Add CS to supply tank.

8 Add VS to supply tank.

9 Let supply tank mix for 5 min.

10 Take samples from supply tank.

11 Start logging flowmeter and scale data.

12 Begin flow into weir tank and monitor flowmeter.

13 Sample overflow from weir tank every 30 s.

14 Begin pumping overflow in the receiving tank.

15 Turn pump and paddles for the receiving tank.

16 Once empty, turn off pump and paddles for the supply tank.

17 Ensure all overflow is included in receiving tank after overflow stops.

18 Let receiving tank run for 5 min.

19 Take samples from receiving tank.

2.2.2 Sampling methods

The overflow weir (Figure 6) was sampled directly using three different 

sampling devices to identify any potential biases in sediment 

concentrations and grain size distributions between sampler types. A 

total of nine tests (B-J) were conducted, grouped by the percentage fines 

(< 63 μm) in the sediment mixtures (Table 2). For each test, a sample 

was collected approximately every 20 s, which yielded approximately 14 

samples per test for a 5 min overflow period. Half of these samples were 

used to determine sediment concentration by mass while the other half 

were used for grain size analysis and determination of the fraction of 

fines. Two samples (~ 0.5 L each) were also collected at the receiving 

tank for comparison against the overflow samples. 
ERDC/CHL TR-20-15 13

Figure 6. Model weir tank in overflow. 

Table 2. Test matrix for weir overflow sampling. 

% Fines Test ID Sampler Type 

0.1 H Bottle

0.1 I Box

0.1 J Tube and Hopper Pipe Sampling

0.2 B Bottle

0.2 C Box

0.2 D Tube

0.2 K Hopper Pipe Sampling

0.3 E Bottle

0.3 F Box

0.3 G Tube

The sampling devices consisted of a bottle sampler, a box sampler, and a 

tube sampler (Figure 7). The bottle sampler (Figure 7-A) was simply a 1 L 

Nalgene bottle that was dipped by hand into the overflow. Care was taken 

not to overfill the bottle, which could bias the sample; any overfilled 

bottles were discarded then resampled. 
ERDC/CHL TR-20-15 14

Figure 7. Three weir overflow sampling devices: (a) bottle, (b) box, and (c) tube. 

The box sampler (Figure 7-B) was designed to take an integrated sample 

through a column of the overflow. The narrow design and thin side walls 

were meant to minimize turbulence and allow for isokinetic (undisturbed 

flow) sampling of the design flow velocity. A bottle was used to collect 

samples from the outflow port as flow was continuously passed through 

the sampler for the duration of overflow. The tube sampler (Figure 7-C) 

consisted of a vertical array of metal ports that were tapered and thinning 

in the direction of incoming flow. The ports directed flow into a vertical 

tube with an outflow port at the bottom for sample collection. Like the box 

sampler, the tube sampler rested on the lip of the weir allowing flow to 

pass through continuously while samples were taken at the outflow port.

2.2.3 Dredge hopper

A significant challenge of the project was to capture representative 

sediment samples from the hopper. While sampling the hopper bed during 

the loading cycle, special attention was necessary to minimize bias 

introduced from any sampling technique used. 

Three general techniques were proposed to capture representative hopper 

samples: (1) collect samples via vibracoring once dredging had ceased, (2) 

collect samples from the collapsing side wall of sediment during pump-out 

operations, and (3) collect samples from the rising bed surface during the 

loading cycle. The vibracoring Option 1 was eliminated based on safety 

concerns of conducting such an operation on the dredge deck, as well as 
ERDC/CHL TR-20-15 15

concerns about achievable penetration depth. Option 2 was considered 

viable, but the question of the number of samples needed, and the 

distribution of sample locations to achieve sample representativeness, 

remained. Thus, Option 3 was decided to be safer than the vibracoring 

method while providing the benefits of collecting data spatially across the 

hopper. For these laboratory experiments, two custom devices were tested:

(1) a pipe sampler and (2) a plate sampler. Laboratory tests were designed 

and conducted to evaluate the effectiveness of the samplers, and are 

described in detail below.

2.2.3.1 Hopper pipe sampler

The pipe sampler was a nominal 7.6 cm (3 in.) diameter polyvinyl chloride

(PVC) pipe, 15.3 cm long, and closed at one end with a total volume of 

approximately 1.5 L. The pipe sampler was attached to a pole and lowered 

to the sediment surface for 15 s (Figure 8), which would fill the sampler 

based on a typical vertical bed rise velocity of 5 mm/s within a prototype 

hopper. After each collection, the contents of the sampler were emptied 

into a bucket and composited to obtain a bulk size distribution and 

percentage of fines that should represent the average composition in the 

tank. Two trials were conducted using the pipe sampler (Table 2, Tests J 

and K). For each trial, three to four samples were collected and 

composited for grain size analysis. 

For comparison, the weir tank was also cored using a 10 cm diameter

polycarbonate tube. The composition of this core was treated as being 

closer to the true representation of the sediment. Surface fines retained in 

the core were discarded to make a proper comparison.
ERDC/CHL TR-20-15 16

Figure 8. Schematic cross-sectional view of the weir tank with bed samplers. 

Samples were taken during the overflow period as the bed developed and raised, 

which filled the sampler. A core was taken adjacently once the surface water 

had drained. 

2.2.3.2 Plate sampler

The plate sampler consisted of an inner, 10 cm diameter aluminum disk 

and an outer 25 cm diameter ring. Each disk and ring was fabricated in 

two parts that sandwich a strong, flexible, vinyl membrane (Figure 9).

Figure 9. Plan view of the plate sampling device. The fully constructed version with 

chain bridling is shown on the left. 
ERDC/CHL TR-20-15 17

The operational aspects of the sampler are illustrated in Figure 10A-D. The 

low-profile design was intended to eliminate sheltering effects by resting 

flat on the sediment bed until retrieval (A). Under load, the membrane 

flexed and created a shallow bowl to retain the sediment sample (B). The 

contents were exposed for sampling by pushing the plate onto a riser (C). 

Finally, a subsample was taken by pushing a short core with known 

volume to refusal above the center plate (D).

 Figure 10. Generalized operational aspects of the plate sampler. Rest position (A), 

under load upon retrieval (B), and sample recovery position (C and D). 

Chain bridling was attached to the sampler to facilitate deployment. The 

sampling technique consisted of lowering the sampler to the hopper bed, 

waiting a specified period for burial, and then retrieving. Upon retrieval, 

the membrane flexed and created a shallow bowl when full to protect the 

sample from washing out during retrieval (Figure 11). Any remaining 

surface fines that would otherwise cause a positive bias were discarded 

during the subsampling procedure using the short core, which is 

illustrated in detail in Figure 12.
ERDC/CHL TR-20-15 18

Figure 11. Deployment (left) and retrieval (right) of the 

plate sampler in the model hopper tank. 

Figure 12. Image sequence showing the sample recovery process. (1) The sample 

was retrieved, and (2) the inner disk was allowed to rest on a riser that exposed the 

sediment collected on its surface. (3) A short core was inserted to refusal (4), and 

sediment above and around the short core was cleared away (5 and 6). The sample 

was then slid off the disk into a container and then composited (7 and 8). 
ERDC/CHL TR-20-15 19

The plate sampler experiments were conducted independently of the 

previous tests and therefore used a slightly different experiment setup 

which is described below.

Two test mixtures were created using silt/sand ratios of 0.10 and 0.30 

using the VS and FS sediments. Each mixture was batched to 

approximately 635 kg total weight divided into thirty-two 5 gal buckets.

A schematic diagram of the experiment setup is shown in Figure 13. The 

system was designed for continuous flow while maintaining hydraulic 

head in the sediment supply tank. Water was supplied to the sediment 

tank using a small gas powered 5 cm (2 in.) intake semi-trash pump, which 

was then transferred to the weir tank using a similar pump. Flow to the 

weir tank was monitored using an electromagnetic flow meter. Flow rate to 

the weir tank and head within the sediment tank was maintained by 

adjustment of a series of gate valves.

Figure 13. Schematic diagram of the plate sampler experiment design. 

Once the target flow rate (75 gal/min) and desired head were achieved, 

sediment was introduced to the supply tank at a rate of 40 lb/min. The 

plate sampler was then lowered to the bed, and a sample recovered for 

every four buckets of material introduced (enough to be assured the 

sampler was buried). Thus, a total of eight samples were recovered for 

each test. Samples were recovered at the same position midway of the tank 

(Figure 13, plan view). Once all the sediment was introduced, flow was 

stopped and a 5 cm (2 in.) diameter core was taken at the opposite side of 

the plate sampler (Figure 13, plan view). The contents of the core were 
ERDC/CHL TR-20-15 20

emptied into a bucket, except for the upper 5 cm at the sediment-water 

interface to avoid biasing the sample with fines from the overlying water 

column (Figure 14). Core recovery for test 1 (10% fines) was approximately

90%, while for test 2 (30% fines) core recovery was approximately 60%.

Figure 14. Recovered core used to compare 

against composited bed samples.

2.2.3.3 Sample analysis

The sediment from the composited bed samples and core was dried in a 

50°C oven for 24 hr, then prepared for mechanical sieving. Observations 

of the dried sediment noted the presence of aggregated silt. As a 

consequence, it was necessary to mechanically agitate the samples using a 

rubber-tipped pestle to break apart the aggregates until they were no 

longer observed. The sediment was then split using a riffle splitter to a 

target mass of approximately 50 g and mechanically sieved at the 

sand/fine boundary using a no. 230 (63 μm) sieve. The percentage by 

weight passing the no. 230 sieve was taken as the percentage of fines in the 

sample. The composition of the core was treated as the true but unknown 

value from which to compare the composited bed samples and determine 

the percentage error.
ERDC/CHL TR-20-15 21

2.3 Hydraulic splitting of sediment-water mixtures

This section considers the use of a large recirculating tank for the 

purpose of splitting sediment-water mixtures. Inflow and/or weir 

sampling could involve the capture of 30 to 60 L of slurry per load that 

would then have to be reduced (via sample splitting or subsampling) to a 

manageable volume or mass for laboratory analysis. Existing hydraulic 

means (such as cone or churn splitters) for splitting of suspended 

sediment samples containing sand are prone to bias associated with the 

rapid settling of sand. Further, they are not practical for splitting large 

volumes at high sediment concentration. These tests explored whether or 

not subsamples extracted from the tank would be reliably characteristic 

of the population contained within.

2.3.1 Recirculating tank system

The recirculating system consisted of a 377 L (100 gal) semi-conical tank 

outfitted with a flexible nominal 5 cm (2 in.) suction line attached to a 

trash pump with a flow capacity of 9.5 L/s (150 gal/min) (Figure 15). The 

suction line ran from the bottom of the tank to the return line, which was a 

vertical section of 5 cm (2 in.) diameter PVC pipe that was routed back into 

the tank via a through-wall connector. Attached to the terminating end of 

the return line was a metal diffuser to disperse the sediment mixture. Two 

ports were installed from which to draw samples, one off the middle of the 

tank and one off the return line. The intake side of the mid-tank port ran 

to the center of the tank and had an open-ended tee attachment to restrict 

the sampling zone and minimize sample bias. The return line port was 

located in the vertical section of the return line. The placements of the 

sampling ports were based on locations of high turbulence to allow for 

increased mixing efficiency. The flow rate was monitored using an in-line 

electromagnetic flow meter.
ERDC/CHL TR-20-15 22

Figure 15. Recirculating tank schematic for hydraulic sample splitting. 

2.3.2 Sediment mixtures and schedule

Sediments used in the tests consisted of CS, FS, and VS sediments 

(Table 3). Grain size characteristics for these three sediments were 

provided in Section 2.1. A total of six tests were conducted. The sediment 

mixtures for tests 1–3 were the construction sand (CS) and silt (as 

previously described) with silt content of 0.10, 0.20, and 0.30, 

respectively. The mixtures for tests 4–6 were comprised of the same 

sand/silt ratios but used FS in place of CS. Five replicate samples were 

collected for each test. The target dry sediment mass introduced to the 

system was 19 kg to obtain an average sediment concentration by mass in 

the tank of 50 g/L. Care was taken to ensure that the sediment 

concentration in the tank was accurately quantified. As such, sediment 

masses were weighed to the nearest gram, and for each sediment type the 

average moisture content was obtained by evaporation to account for the 

additional water volume. Water volumes pumped into the tank system 

were measured to the nearest gallon (with accuracy of +/-1%) using the 

flow meter. 
ERDC/CHL TR-20-15 23

Table 3. Sample splitting test matrix. 

Test No. Test ID Sand 

type 

% Sand / 

%Silt Sample method 

1

A1 CS 90/10 Mid tank spigot

A2 CS 90/10 Tank return line

2

B1 CS 80/20 Mid tank spigot

B2 CS 80/20 Tank return line

3

C1 CS 70/30 Mid tank spigot

C2 CS 70/30 Tank return line

4

D1 FS 90/10 Mid tank spigot

D2 FS 90/10 Tank return line

5

E1 FS 80/10 Mid tank spigot

E2 FS 80/20 Tank return line

6

F1 FS 70/30 Mid tank spigot

F2 FS 70/30 Tank return line

Note: CS refers to construction sand. FS refers to fine sand (see text for median size 

information).

2.3.3 Splitting procedure

First, the recirculating tank was filled with a known water volume, 370 L. 

While at maximum flow (150 gal/min; 9.5 L/s), the target sediment mass 

at the assigned sand/silt proportion was then slowly added. Silt was 

introduced first and mixed for 3 min before the sand was slowly 

introduced. Once the sand was added, the slurry was allowed to mix for an 

additional 5 min to optimize mixture homogeneity. This allowed for 

approximately 7–8 full-volume mixing cycles based on the tank evacuation 

time of 0.66 min. Next, samples were withdrawn from the mid-tank port 

followed by the return line port, each being received into a 1 L bottle. For 

each test, five independent samples were collected at each port for 

repeatability and error analysis. A minimum volume of 0.5 L was collected 

for analysis, and care was taken not to overfill bottles to prevent sample 

biasing (any overfilled samples were noted as such, mostly for a few 

samples at the return line due to its high discharge velocity). Finally, the 
ERDC/CHL TR-20-15 24

remaining slurry was pumped out of the system, and the tank was cleaned 

and prepared for the next test.

2.3.4 Analysis methods

Samples were analyzed for sediment concentration and grain size 

distribution. Sediment concentrations were determined by evaporation 

according to ASTM standards (ASTM 2019). Once the concentrations 

were determined, samples were re-slurried to a minimum volume of 

250 mL and split using a fluorocarbon cone splitter with 10 discharge 

ports (Capel and Larson 1995; Wilde et al. 2014). Aliquots from 3 of the 

10 ports were retained for grain size analysis using a Malvern laser 

scattering instrument.

2.4 Composite sampling of hopper inflow

A numerical experiment was conducted to determine the appropriate 

discrete sampling interval of hopper inflow to achieve a representative 

mean. 

2.4.1 Data source

The data for this analysis were taken from the DQM system for a TSHD 

plant operating along the Florida coast in 2014. The records for 147 loads 

were used for this analysis starting with load 1 on 19 November 2014 and 

ending with load 147 on 28 December 2014. DQM data were recorded on 

average every 7.8 s. While over 30 data metrics are reported, this analysis 

used only the date, time, starboard inflow specific gravity, and starboard 

inflow velocity. The inflow specific gravity was used to calculate the mass 

concentration (g/L). Figure 16 provides the inflow velocity and mass 

concentration for load 93, a typical load based on observation. The dredge 

made two passes on this load with a pause in dredging identifiable by the 

inflow velocity falling to nearly zero and specific gravity equal to unity 

between 20:45 and 21:20. No information was provided in the DQM 

system for sediment gradation; thus, this analysis only considered the 

concentration into the hopper.
ERDC/CHL TR-20-15 25

Figure 16. Recorded starboard velocity and specific gravity for hopper load 93. 

2.4.2 Analysis methodology

For each load, the total sediment input, M, into the hopper through the 

starboard inflow was found by numerically integrating the mass flux. The 

sediment mass flux was calculated as the product of the instantaneous 

volume flux, Q, and mass concentration, C, (estimated from slurry 

density). This numerical integration used the trapezoidal rule as shown in 

Equation 2-3, and assumed the volume flux, Q, was equal to the DQM 

reported port inflow velocity.

MM = ∑ (QQnn−1×CCnn−1)+(QQnn×CCnn)

2

∆tt nn

1 (2-3)

Any DQM data point where the inflow velocity was less than 30.5 cm/s

was not included as this indicated the dredge was not actively dredging. 

Finally, the average sediment mass concentration for the entire load, CC�,

was found by dividing the integrated sediment mass, M, by the integrated 

volume, V. The integrated volume was found using Equation 2-4.

VV = ∑ (QQnn−1)+(QQnn)

2

∆tt nn

1 (2-4)
ERDC/CHL TR-20-15 26

The first methodology assumed samples were taken at specific intervals. 

For example, starting with the first sample and choosing every 20th

sample results in a time interval of 156 s. These selected samples were then 

averaged to compute an average concentration without any consideration 

of the flowrate. However, an additional comparative dataset can be found 

by starting at the second sample and choosing every 20th sample, akin to 

applying a phase shift. Figure 17 shows this sampling strategy being 

applied to load 93 with the sampled points for no phase shift (Subset 1) 

and a phase shift of 10 (Subset 2) with a sampling interval of 156 s, or 

every 20th sample. Thus, this methodology found the average mass 

concentration for a load for every possible interval up to 600 considering 

every possible phase shift, and is referred to as “fixed interval” in results.

Figure 17. Example of subset sampling Load 93. A fixed sampling interval with no 

phase shift (Subset 1) and a phase shift of 10 (Subset 2). 

The second methodology assumed random sampling intervals. For 

example, a sample size of 20 may have been chosen for a load that takes 

20 min to dredge. These samples were pulled randomly but not uniformly 

in time. The average sampling interval was the length of dredging record 

divided by the number of samples, or in this example, 60 s. These 

randomly sampled concentration measurements were averaged and 

compared to the correct average concentration. As with the previous 

sampling method, no consideration for the associated flowrate for each 

sample was given. However, one random sampling does not provide a 

strong comparative point, but it is possible to randomly sample the set 

creating many realizations. Figure 18 is an example of two subsets for 

load 93 using this methodology. This methodology finds the average 

concentration for a load for 100 random perturbed realizations for every 

average sampling interval up to 600 s and is referred to as “random 

interval” in the results.
ERDC/CHL TR-20-15 27

Figure 18. Example of two subset samplings of load 93. Two random sampling 

realizations with average sampling interval of 156 s. Note that the samples are 

pulled randomly, not at a fixed sampling interval. 

The averages of the sampled concentrations were compared to the correct 

average mass concentration given by using Equation 2-3 and 2-4, and the 

percent error, E, was calculated using Equation 2- 5. 

EE = 100 × �CC̅

ssssssssssssss−CC̅cccccccc cccc�

CC̅

cccccccc cccc

(2-5)

This procedure was repeated for many realizations of each sampling 

strategy over 147 hopper loads of data, resulting in a probabilistic estimate 

of the expected errors associated with each sampling and compositing 

strategy. The mean absolute error, EE� for all 147 loads for a given time 

interval, was calculated by taking the average percent error from each load 

for each sampling interval. 

EE�(tt) = 1

nn ∑ EEnn(tt) 147

nn=1 (2-6)

The bias was calculated by the same method as above for the relative error 

instead of the percent error. Additionally, for a given sampling interval all 

the errors were used to populate a lognormal distribution that was used to 

calculate the 95% standard error for a given load. A lognormal distribution 

was chosen because the percent error could never be negative whereas a 

normal distribution would allow for some percentage of the results to have 

a negative percent error. Two parameters are needed to quantify a 

lognormal distribution: (1) the mean, μ, and (2) standard deviation, σ, of 

the variable’s natural logarithm. The variance, or square of the standard 

deviation, can also be used. These values were combined from each load to 

define a lognormal distribution that represented the absolute error for 

each sampling interval. This was achieved by taking an average of the 

lognormal distribution means, μ, and combining the variances, σ2. 
ERDC/CHL TR-20-15 28

3 Results

This chapter presents the results of laboratory and numerical testing, and 

analysis aimed at addressing the sampling and analysis plan for 

conducting field sampling to address sediment sorting and separation 

during hopper dredging and placement operations. 

3.1 Physical sampling

3.1.1 Weir overflow results

The sediment passing the overflow weir consisted mostly of fines, which 

comprised 95.5% ± 1.3% (mean ± standard deviation) of the total sample 

averaged across all tests. The fines content for each test was analyzed to 

discern differences between sampling devices, as well as differences 

between the numerically averaged overflow samples and composited 

receiving tank samples. 

Figure 19 shows there was little difference between the average percent 

fines from individual weir samples and the composited value obtained 

from receiving tank samples (95.9% ± 0.2%), which also showed little 

variability irrespective of initial fines content of the starting mixture (10%, 

20%, 30%). Likewise, there was little variability in the fines percentage 

between sampling devices (Figure 19). 

Results from the analysis of sediment concentrations for all experiments 

are summarized in Table 4. Sediment concentrations showed little 

variability between sampling devices (Figure 20). The largest uncertainty 

in concentration (mean ± standard error of the mean) between sampling 

devices occurred for the tests using 30% fines, which increased slightly 

from 124±4, 128±3, and 133±2 g/L for bottle, box, and tube methods, 

respectively. Since the percentage of fines over the weir was nearly 

uniform at 95%, the measured concentrations tended to increase 

proportionally to the percent fines of the starting mixture from the supply 

tank, also with little variability between the overflow and receiving tank 

(Figure 21). 

Except for the box sampler, no systematic trend in concentration was 

detected between sampling methods with increasing fines content of the 

mixtures (Figure 22). The standard deviation in concentration of the box 
ERDC/CHL TR-20-15 29

sampler increased with increasing fines content, from 1.6 to 5.2 to 8.4 g/L 

for mixtures with 10%, 20%, and 30% fines, respectively.

Figure 19. Results of weir sampling tests, average percent fines between 

weir overflow samples and receiving tank samples. Sampling method only 

refers to the overflow weir. 

80

85

90

95

100

Percent fines

Starting Mixture: 20% Fines

80

85

90

95

100

Bottle Box Tube

Percent fines

Sampling method at overflow weir

Starting Mixture: 30% Fines

Weir overflow Receiving tank

80

85

90

95

100

Percent fines

Starting Mixture: 10% Fines

A.

B.

C.
ERDC/CHL TR-20-15 30

Table 4. Summary table of sediment concentrations for each experiment. 

Experiment IDs annotated with R refer to receiving tank samples while those 

with W refer to weir tank samples. Std Dev refers to standard deviation, and 

Std Error refers to the standard error of the mean. 

Figure 20. Average concentration for the different 

methods of weir overflow sampling and receiving tank. 

Experiment ID n samples % fines Sampling method Mean C (mg/L) Std Dev Std Error

BR 2 20% Bottle 85.24 1.28 0.90

BW 6 20% Bottle 82.39 4.86 1.99

CR 2 20% Box 88.64 1.16 0.82

CW 7 20% Box 85.86 5.23 1.98

DR 2 20% Tube 87.96 0.11 0.07

DW 6 20% Tube 82.49 18.03 7.36

ER 2 30% Bottle 125.54 0.35 0.25

EW 7 30% Bottle 123.99 9.66 3.65

FR 2 30% Box 131.36 0.65 0.46

FW 6 30% Box 127.52 8.37 3.42

GR 2 30% Tube 130.77 0.77 0.55

GW 6 30% Tube 132.52 5.93 2.42

HR 2 10% Bottle 42.46 0.71 0.50

HW 7 10% Bottle 38.83 10.12 3.83

IR 2 10% Box 40.79 0.64 0.45

IW 6 10% Box 42.02 1.62 0.66

JR 2 10% Tube 43.67 0.91 0.65

JW 6 10% Tube 44.32 2.78 1.13

0

50

100

Mean C [mg/L]

Starting Mixture: 20% Fines

110

115

120

125

130

135

140

Bottle Box Tube

Mean C [mg/L]

Sampling method

Starting Mixture: 30% Fines

Receiving tank Overflow weir

0

50

100

Mean C [mg/L]

Starting Mixture: 10% Fines A.

B.

C.
ERDC/CHL TR-20-15 31

Figure 21. Mean concentration for all sampling methods for weir overflow and 

receiving tank samples. 

Figure 22. Variability of concentration for each weir overflow sampling method. 

Relative errors (RE) between sample mean concentrations and receiving 

tank concentrations are provided in Table 5. Here, the tank mean was 

considered the true or expected value. The RE of any sampler was within 

10%. On average the concentrations from the weir samples were lower 

than expected (6 out of 9 cases). Computing the mean relative error (MRE) 

for each sampler (Table 5) shows that the bottle sampler had the greatest 

deviation from the expected value (-4.4%) compared to the box and tube 

samplers that had MRE of -1.0% and -1.1%, respectively.

0

20

40

60

80

100

120

140

10% 20% 30%

Mean C [mg/L]

Initial percent fines

 

Receiving tank Overflow weir

0.00

5.00

10.00

15.00

20.00

Standard deviation [mg/L]

Bottle Box Tube

 

y p g 

10% 20% 30%
ERDC/CHL TR-20-15 32

Table 5. Summary table comparing the RE in concentrations between the weir 

samples and the mean value in the receiving tank for all sediment mixtures and 

sampling devices. 

Test % 

fines Method Tank mean (g/L) N Weir mean (g/L) N MRE (%) 

10 Bottle 42.46 2 38.83 6 -8.6

10 Box 40.79 2 42.02 6 3.0

10 Tube 43.67 2 44.32 7 1.5

20 Bottle 85.24 2 82.39 6 -3.3

20 Box 88.64 2 85.86 7 -3.1

20 Tube 87.96 2 82.49 6 -6.2

30 Bottle 125.54 2 123.99 7 -1.2

30 Box 131.36 2 127.52 6 -2.9

30 Tube 130.77 2 132.52 6 1.3

Method MRE (%)

Bottle -4.4

Box -1.0

Tube -1.1

3.1.2 Hopper sampling

The percentage fines of sediment retained in the hopper was compared 

between the pipe sampler and corer for two starting mixtures (10% and 

20%). For each case, the composited sediment collected by the pipe 

sampler was unable to match the fines content measured by the core 

sample. The fines content was overestimated by 111% for the starting 

mixture of 10% fines and underestimated by 57% for the starting mixture 

of 20% fines. (Figure 23). The sediments collected by the corer are 

considered the true composition; however, note that the percent fines 

from Tests J and K did not double despite a doubling of fines of the 

starting mixture from 10% to 20%. Similarly, the percent fines captured by 

the pipe sampler were similar between tests (3.5% and 3.2%) despite a 

doubling of fines of the starting mixture.
ERDC/CHL TR-20-15 33

Figure 23. Comparison of the percentage fines retained in the hopper tank 

collected by the pipe sampler and a core for two test cases. 

3.1.3 Hopper sampling via plate sampler

The percentage fines captured by the plate sampler was 5.4% for the 10% 

silt mixture and 6.2% for the 30% silt mixture (Figure 24). That is 

compared to 4.3% and 7.7% fines captured by the cores for the same 

mixtures, respectively. Therefore, the plate sampler slightly overestimated 

the fines content for the 10% silt mixture while it slightly underestimated 

the fines for the 30% silt mixture. This represents an absolute error of 

20%–25%. However, statistical significance cannot be established due to 

the limited number of experiment runs.

Figure 24. Results comparing the percentage fines captured using the plate 

sampler and a 2 in. diameter coring device. 
ERDC/CHL TR-20-15 34

3.2 Hydraulic sample splitting

Results from the sample splitting experiments were used to determine if 

the sediment characteristics (concentration and size distribution) of 

hydraulically withdrawn aliquots from a recirculating tank are 

representative of the known concentration and composition of a slurry 

mixture (Table 3). The sediments used in the experiments (CS, FS, and VS) 

are the same as previously described. See Section 2.1 for percentile sizes 

and gradation curves.

3.2.1 Sediment composition

A summary of the sediment size characteristics, percent sand, and percent 

mud for each test is provided in Table 6. From examining the ratios of the 

sand-to-mud content before and after sample collection, the mud contents 

are often similar or over-represented in the CS tests and under-represented 

in the FS tests.

Table 6. Averaged sediment characteristics of samples collected from the mid-tank 

port (T) and the return line port (R). Initial mud/sand ratios represent the starting 

sediment mixture for a given test followed by ratios after sampling. IDs appended 

with C refer to construction sand tests and with F refer to fine sand tests. 

ID Sand 

Type 

DD11

(μμμμ) 

DD55

(μμμμ) 

DD99

(μμμμ) 

Sand 

% 

Fines 

% 

Initial 

Mud/sand 

Final 

Mud/sand 

T10C CS 25 339 619 81.1 18.9 0.11 0.23

R10C CS 199 387 665 90.1 9.9 0.11 0.11

T20C CS 18 293 574 70.0 30.0 0.25 0.43

R20C CS 33 341 603 82.7 17.3 0.25 0.21

T30C CS 11 127 493 48.1 51.9 0.43 1.08

R30C CS 20 357 625 76.5 23.5 0.43 0.31

T10F FS 110 194 322 96.4 3.6 0.11 0.04

R10F FS 122 210 351 98.0 2.0 0.11 0.02

T20F FS 92 182 313 93.1 6.9 0.25 0.07

R20F FS 104 186 312 95.4 4.6 0.25 0.05

T30F FS 27 162 307 83.1 16.9 0.43 0.20

R30F FS 43 178 328 88.2 11.8 0.43 0.13

Averaged sediment characteristics of samples collected from the mid-tank port (T) and the return line port (R). Initial 

mud/sand ratios represent the starting sediment mixture for a given test followed by ratios after sampling. IDs appended 

with C refer to construction sand tests and with F refer to fine sand tests. Percentile grain diameters in red highlight 

significant deviation from the average.
ERDC/CHL TR-20-15 35

3.2.2 Sediment concentration

Sediment concentrations between the mid-tank port and return line port 

were markedly different. Figure 25 shows a bar graph of the average 

concentrations for each mixture and sampling port. The dashed line 

designates the known system concentration of 50 g/L. For each test, 

concentrations showed little variability (N = 5) at either sampling port, 

though the standard error of the mean (SEM) was slightly higher for 

samples collected at the return line; values ranged from 0.4-0.8 g/L at the 

mid-tank port and from 1.1-3.1 g/L at the return line port. 

The data are further reduced in Figure 26 and provide a good summary 

of the results. Overall, sediment concentrations collected at the mid-tank 

port averaged 40 ± 2 g/L for the coarse sand tests and 45 ± 1 g/L (mean 

± SEM) for the fine sand tests and were therefore closest to the known 

concentration of 50 g/L. Still, these values represent respective errors of 

19% and 11%. In contrast, sediment was much more concentrated in the 

return line port, which averaged 117 ± 5 g/L and 75 ± 4 g/L (mean ± 

SEM) for the coarse and fine sand tests, representing errors of 134% and 

50%, respectively.

Figure 25. Sediment concentrations averaged by test. Error bars represent the SEM. 

T = tank port, R = return line port, F = fine sand, and C = construction sand. Dashed 

line shows the known system concentration. 
ERDC/CHL TR-20-15 36

Figure 26. Sediment concentrations averaged by sampling port and sediment type. 

Error bars represent the averaged SEM. Dashed line shows the known 

system concentration. 

Sand and mud concentrations were determined by multiplying the mean 

concentration of a given test by its fraction of sand or mud (Figure 27). 

The sampled concentrations from each test can then be compared to the 

expected concentrations of sand and mud (Figure 27; E10, E20, and E30). 

Due to sand’s settling velocity, the concentration of sand was expected to 

be slightly higher in the rising flow of the return line and slightly lower in 

the descending flow of the tank. The relative magnitude of these 

concentration variances increased with settling velocity and decreased 

with flow speed in the return line. For the testing configuration, the sand 

concentration biases were expected to be on the order of a few percent. 

Due to the slow settling velocity of fine sediment, the concentration of fine 

sediment was expected to be very close to equal in the return line and 

tank. The results presented in Figure 27 show much more variation in both 

total concentration and fractional concentration than expected. The total 

concentration in the return line was much higher than expected, and the 

mid-tank total concentrations were similarly lower than expected. These 

observations suggest that there could be inadequate mixing by the tank 

diffuser and, perhaps, gravity flow down the tank walls that bypasses the 

mid-tank sampling position. This flow down the tank walls would also 

concentrate sediment at the bottom of the conical tank and increase 

sediment concentration in the return line. The variations from expected 

values in mud concentration are likewise unexpected. The measured mud 
ERDC/CHL TR-20-15 37

concentrations vary by more than a factor of two, both higher and lower, 

from the expected values.

Figure 27. Averaged concentrations of mud (dashed pattern) and sand (dotted 

pattern) for each test grouped by initial mud content (10%, 20%, 30%). T = tank port, 

R = return line port, C = construction sand, and F = fine sand. For comparison, the 

expected concentrations of sand and mud are also plotted (E10, E20, E30). 

The underlying principles of the large-volume hydraulic splitter are sound. 

The testing results presented here highlight the difficulty in splitting 

suspended sediment samples, particularly those with fast-settling 

particles. Further testing of the concept in the future is recommended with 

particular attention given to redesign of the flow diffuser in the upper 

portion of the tank, and sample analysis methods for the sand/fine split. 

Alternatively, samples with fast settling particles can be dewatered and 

split in a moist state.

3.3 Numerical experiments

To determine appropriate sampling methods and intervals for the dredge 

inflow, a numerical experiment was undertaken. Figure 28 provides the 

mean and 95% confidence intervals of the absolute relative error in mass 

concentration for both fixed and random interval sampling. The mean 

absolute RE of the mass concentration was approximately 3% smaller for 

the fixed interval sampling versus the random interval sampling. The 95% 

interval error was approximately 15% larger for the random interval 

sampling versus the fixed sampling for any average sampling interval over 
ERDC/CHL TR-20-15 38

200 s. At a sampling interval of 60 s, a 4% error was introduced with the 

fixed interval sampling compared to 7% for the random interval sampling. 

Both sampling methods showed a mean absolute error of less than 10% 

with a sampling interval less than 200 s. Even at sampling intervals less 

than 30 s, error was present on the order of 4%. This error was the result 

of the difference between the first moment of mass flux (the true measure 

given by Equation 3) and the arithmetic mean (an approximation of the 

true measure). Additionally, the fixed interval and random interval 

methods produced a relative bias of -1.36% and -1.23%, respectively, for 

the calculated average concentration.

Figure 28. Results of numerical experiment of inflow sampling interval, showing the 

mean absolute error and the 95% interval percent error for both the fixed and 

random interval sampling. 
ERDC/CHL TR-20-15 39

4 Discussion and Conclusions

The goal of this study was to evaluate specific sediment sampling and 

measurement techniques to be applied on TSHDs to determine the 

fraction of fine sediments present at various stages of the dredging 

process. Several specific sampling-related topics were explored, including

the following: 

• determining whether samples from the TSHD can be composited (or 

combined) to form physically averaged samples

• testing a hydraulic means of subsampling large-volume, composited 

samples

• determining suitable sampling methods for collecting samples within 

the dredge from the inflow slurry, the hopper sediment bed, and the 

hopper overflow

• determining the appropriate sampling interval for the hopper inflow.

These research topics were evaluated through a set of laboratory and 

numerical experiments described in previous sections. A discussion of the 

results of the laboratory and numerical experiments is provided in this 

section. Particular emphasis in the discussion is given to recommendations 

for a field data collection campaign to quantify the separation of sediments 

during the dredging and beach placement processes.

4.1 Sample compositing

Sample compositing (or physical averaging) is a method by which samples 

are collected in time, space, or both, and physically mixed to form an 

averaged sample. An inherent assumption in arithmetic averaging is the 

uniform weighting of samples (all samples are equally valued). For the 

proposed field study, sample compositing is considered for hopper inflow 

sampling, hopper bed sampling, and beach coring. 

A primary concern with compositing hopper inflow samples is that the 

covariance of hopper inflow rate and slurry concentration can contribute 

to sample bias. Bias is introduced by arithmetic averaging (physical or 

numerical) of inflow concentration, instead of from the first moment of 

the inflow sediment mass flux. A numerical experiment was conducted to 

determine the error introduced by compositing samples, including the 

effects of sampling interval and regularity. The numerical experiment 
ERDC/CHL TR-20-15 40

resampled data of hopper inflow rate and slurry density with two sampling 

schemes and a range of sampling intervals, for the purpose of determining 

the difference between the arithmetic mean of slurry concentration and 

the true value of mean slurry concentration (as estimated by the first 

moment of sediment mass flux). The results of the numerical experiment 

indicated a small mean error (or bias) on the order of -1%. (In this case, 

negative bias means that the arithmetic mean of the composited sample is 

less than the true value estimated from the first moment of sediment flux.) 

The small bias indicated by the analysis suggests that compositing of the 

physical inflow samples for concentration and size analysis is appropriate.

4.2 Sample splitting

Sample compositing often results in sample volumes or masses that are 

too large for the intended laboratory sample analysis methods. In these 

instances, the sample must be split in a representative manner without 

introducing bias. There are well-documented procedures for splitting of 

dry and moist soil and sediment samples. However, suspended sediment 

samples present particular challenges since the settling velocity of coarse 

sediments such as sand and gravel is sufficiently large to interfere with 

complete and unbiased hydraulic mixing of the sample. Inadequately 

mixed suspensions generally result in bias, as the sample may be 

withdrawn either from a sediment-rich or sediment-poor portion of the 

suspension and will not be representative of the population.

This study attempted to configure a hydraulic sample splitter for the 

purposes of splitting composited hopper bed, hopper overflow, and/or 

hopper inflow samples. The hydraulic splitter was tested with mixtures of 

sand and silt. The results of the hydraulic sample splitter indicated that 

coarser sediments are inadequately mixed by the present design. The 

biases in the return line sample are suspected to be associated with 

inadequate mixing of the sample by the flow diffuser in the upper tank, 

and consequent gravitational settling and concentration of the coarser 

sediments in the bottom section of the conical tank. Concentration of the 

sample in this location resulted in increased concentration in the return 

line and relatively sparse concentration of coarse sediment near the midtank withdrawal point. The conclusion of this work is that the present 

design of this system is inadequate for the requirements of the present 

study, and alternate approaches will be more appropriate.
ERDC/CHL TR-20-15 41

The preferred approach for the field study is to settle and decant water 

from any suspended sediment samples from the composited samples and 

quantify sediment mass in the decanted water. Suspended solids would be 

quantified by filtering decanted water through large glass-fiber filters. The 

settled sediments could then be subsampled in a moist or dry state, which 

is much less prone to particle-settling-related biases.

4.3 Sampling methods

Sampling methods were tested for acquiring samples from the hopper 

outflow weir, the hopper sediment bed, and the hopper inflow.

4.3.1 Hopper overflow weir sampling

Three sampling devices (bottle, box, tube) were tested to determine 

applicability for sampling at hopper overflow weirs. Each device was tested 

in a controlled laboratory experiment aimed at quantifying the suspended 

sediment concentration and size fractionation of a sediment suspension 

passing with similar depth and flow velocity as a prototype hopper 

overflow weir. These tests served to identify advantages and disadvantages 

of one design over another and to anticipate potential issues that might 

arise when deployed on a dredge. 

All three sampling devices provided very similar estimates of average 

concentration and mud content when compared to samples from the 

recovery tank. These favorable evaluations suggest that, when the flow 

depth and flow velocity of the weir are comparable to the testing 

conditions, any of the sampling methods would be appropriate. For 

deeper depths of flow, the bottle sampler may be prone to overfilling and, 

therefore, bias. The box and tube samplers are readily scalable to provide 

sampling over the full depth of overflow. While the preference for one 

sampler over another may only depend on the unique operating logistics 

of a dredging vessel, there is reason to think that pump-sampling (via the 

box or tube sampler) may offer significant advantages. For example, 

Kerssemakers (2004) used custom bottle and flow-through samplers to 

collect samples from a standpipe-style overflow weir aboard the TSHD 

Cornelia. This work clearly demonstrated the challenges of collecting 

overflow samples. It was uncertain whether their devices were capturing 

representative samples due to either overfilling (in the case of the bottle 

sampler) or sampler positioning within the weir. With the box and tube 

samplers, there is no concern of overfilling, and both are more likely to 
ERDC/CHL TR-20-15 42

capture a depth-integrated sample of the overflow (especially the box 

sampler) than the bottle sampler. Additionally, a sample could be drawn 

continuously by attaching a suction line to the discharge outlet from 

which to draw samples. This would allow for greater flexibility in setting 

sampling intervals, which is an important consideration for compositing 

purposes.

4.3.2 Hopper sediment bed sampling

The preliminary design for a hopper sampler consisted of pipe with one 

capped end resting on its side (pipe sampler), as described in Section 3.3. 

During testing, it was noted that sampler orientation had a marked effect 

on sediment capture. Sediment was captured sufficiently only when the 

sampler was oriented parallel to the primary direction of flow (Figure 8). 

Results from two independent tests indicated a sampling bias by 

preferential collection of fine sediments relative to that collected by an 

adjacent core from the bed. The suspected cause of the bias was attributed 

to (1) a sheltering effect by the pipe that allowed suspended fine sediments 

to settle within the sampler and/or (2) sub-maximum filling of the 

sampler that allowed suspended fines to be collected in the overlying water 

within the sampler during retrieval. The limited testing of the pipe 

sampler indicated that its characteristics were unsuitable for sampling the 

hopper bed.

Given the unsatisfactory performance of the pipe sampler, a plate sampler 

was designed and constructed to address sample bias from sheltering 

effects. The operational concept was proven in the laboratory experiments 

and suggests that bed samples from a dredge hopper can be reliably 

obtained in a consistent manner. 

The apparent bias in the fraction of fines obtained using the plate sampler 

was both positive and negative compared to cored samples. These 

differences cannot be explained with any statistical significance given the 

constraints on the number of trials conducted. However, the results 

showed much better agreement compared to those derived using the pipe 

sampler. Although more trials would be necessary to fully evaluate the 

plate sampler, it remains a viable option for collecting representative 

hopper samples from the dredge. Other devices considered (though not 

tested here) to collect samples from the hopper bed were surface grab 

devices and gravity corers. 
ERDC/CHL TR-20-15 43

The Ponar sampler is a clamshell-style gravity sampler that has opposing 

jaws to take surficial sediment samples to a depth of approximately 10 cm. 

They are often equipped with top-facing rubber flaps to allow water to pass 

through upon descent. They are easy to operate, but the major 

disadvantages envisioned are (1) potential for premature closing in high 

turbulence environments, (2) loss of sample due to incomplete closing 

(usually with sandy, coarse sediments), and (3) high propensity of biasing 

during retrieval (not completely shielded). Grab samplers are particularly 

susceptible to washout of fine-grained sediment (FieldsCapri and 

Schumacher 2004). Based on these factors, the Ponar sampler was 

eliminated as a viable sampling option.

Gravity core samplers are weight-assisted coring devices used to take 

vertical profiles of the sediment. The sediment is contained within a 

polycarbonate tube equipped with a core catcher to aid in sample recovery. 

They are most often used for soft, loosely consolidated fine-grained 

sediments. However, the sandy sediment within the upper layers of the 

dredge hopper bed may be fluidized enough to allow for sufficient 

penetration, and therefore the gravity core sampler remains a viable 

sampling option.

4.3.3 Hopper inflow sampling

Collecting samples from the hopper inflow would be achieved using a 

pump sampling device. The intake of the sampling hose would be 

positioned directly within the inflow discharge. Slurry would be withdrawn 

from the dredge inflow with an engine-driven trash pump. Samples would 

be collected from the trash pump discharge on a periodic basis from the 

trash pump effluent. Proper testing of a sampler for this purpose was not 

feasible in the laboratory due to the large discharge volumes expected at 

the dredge inflow. 

Primary concerns of inflow sampling are the potential biasing of inflow 

samples by compositing of samples and excessive error introduced by 

inadequate sampling of the inflow. The sample compositing concern was 

addressed through a numerical analysis (discussed above). The numerical 

experiment also examined appropriate sampling intervals of the inflow. 

Sampling theory indicates that sample approximation of the population 

improves with increased sample size. The numerical experiment indicated 

an improved estimate of the true mean slurry concentration with reduced 

sample interval (equivalent to increased numbers of samples). Regular 
ERDC/CHL TR-20-15 44

sampling in time was clearly better than random sampling in time, 

reducing the mean absolute error by approximately 5% and the upper limit 

of absolute error by 10% to 20%. The gains of regular sampling are 

presumably due to the inherent time variability in the inflow rate and 

slurry concentration. Regular sampling over the entire loading cycle would 

also be important for capturing variations in sediment composition during 

the loading cycle. A mean absolute error less than 10% can be obtained 

with composited samples collected at regular intervals of 120 s or less. If 

the sampling interval is further reduced to 90 s, the mean absolute error 

reduces to less than 5%. These sampling intervals are physically feasible 

with the proposed pump sampling. Additionally, the results of the 

numerical experiment can be applied as an estimate of the expected error 

for the actual sampling intervals performed in the field.

4.4 Conclusions

The findings of the laboratory and numerical evaluations described in this 

study lead to the following conclusions related to field studies:

1. The three devices (box, bottle, and tube samplers) used to measure the 

sediment properties of the hopper overflow generated estimates of 

suspended sediment concentration and size distribution that were, on 

average, within 4% or less relative to samples obtained from the 

recovery tank. The choice of sampling device to apply in a field setting 

is most likely dependent on access to the hopper overflow location and 

characteristics of the overflow such as depth of overflow, velocity of 

overflow, and weir geometry.

2. Numerical evaluation of inflow data for 147 hopper loads indicated that 

compositing of the hopper inflow samples will result in low bias and 

acceptable accuracy. Sample compositing is also acceptable for 

increased sampling of the hopper bed, hopper suspended load, and 

beach coring activities.

3. A hydraulic sample splitter to reduce the volume of composited hopper 

inflow samples was evaluated and found to be unacceptable in its 

capacity to mix sand-sized sediment. All sample splitting for the field 

study should be accomplished by moist or dry sample splitting 

according to established standards and procedures. Suspended 

sediment samples should be settled and decanted prior to sample 

splitting to avoid hydraulic separation and bias.

4. The numerical experiments of the inflow data provided guidance for 

the necessary sampling interval to accurately describe the 
ERDC/CHL TR-20-15 45

concentrations. A fixed interval between samples had less error than a 

random interval, demonstrating the need for regular sampling over the 

entire filling operation. Sampling intervals of 90 to 120 s contribute 

sampling errors less than +/- 5% to 10%, respectively.

5. Sampling the deposited sediment in the hopper requires that the 

method not create a shelter from the flow and turbulence. Sheltering 

increases the percent fines of the sample, thus biasing the results. 

Other important concerns are likelihood of sample recovery, ease of 

use, and safety. Based on these concerns, vibracores, pipe samplers, 

and surface grabs were eliminated as sampling options in the hopper. 

Therefore, the two options considered here that provide the best 

chance of collecting representative hopper samples are the gravity 

corer and the plate sampler.
ERDC/CHL TR-20-15 46

References

ASTM (ASTM International). 2019. Standard Test Methods for Determining Sediment 

Concentration in Water Samples. D3977-97. West Conshohocken, PA.

Capel P. D., and S. J. Larson. 1996. Evaluation of Selected Information on Splitting 

Devices for Water Samples.” USGS Water-Resources Investigations Report 95-

4141. Reston, VA: US Geological Survey.

Dean, R. G. 2003. Beach Nourishment: Theory and Practice. Singapore: World 

Scientific.

FieldsCapri, J., and B. A. Schumacher. 2004. Literature Review and Report: Surface 

Sediment Sampler Database. EPA/600/R-03/115 (NTIS PB2004-101011).

Washington, DC: Environmental Protection Agency.

Florida Department of Environmental Protection. 2017. Florida Administrative Code 62 

B-41.007. Rules and Procedures for Application for Coastal Construction 

Permits. Tallahassee, FL: Department of Environmental Protection, Beaches and 

Coastal Systems Division.

https://www.flrules.org/gateway/ChapterHome.asp?Chapter=62B-41

Kerssemakers, K. A. 2004. Overflow Sampling of Trailing Suction Hopper Dredgers: A 

Case Study on the TSHD Cornelia. MS thesis. The Netherlands: Delft University 

of Technology.

Ousley, J. D., E. Kromhout, M. H. Schrader, and L. S. Lillycrop. 2014. Southeast Florida 

Sediment Assessment and Needs Determination (SAND) Study. ERDC-CHL TR14-10. Vicksburg, MS: US Army Engineer Research and Development Center.

Richardson, J. F., and W. N. Zaki. 1954. “Sedimentation and Fluidization, Part I.”

Transactions of the Institution of Chemical Engineers 32: 35–53.

van Rhee, C. 2001. “Numerical Simulation of the Sedimentation Process in a Trailing 

Suction Hopper Dredge.” Proceedings of the 16th World Dredging Conference, 

Kuala Lumpur, Malaysia.

Wilde, F. D., M. W. Sandstrom, and S. C. Skrobialowski. 2014. “Selection of Equipment 

for Water Sampling” (Ver. 3.1). Book 9, Chapter A2 in Techniques of WaterResources Investigations. Reston, VA: US Geological Survey.
ERDC/CHL TR-20-15 47

Unit Conversion Factors

Multiply By To Obtain 

cubic feet 0.02831685 cubic meters

cubic inches 1.6387064 E-05 cubic meters

cubic yards 0.7645549 cubic meters

feet 0.3048 meters

gallons (US liquid) 3.785412 E-03 cubic meters

microns 1.0 E-06 meters

miles (nautical) 1,852.0 meters

miles (US statute) 1,609.347 meters

miles per hour 0.44704 meters per second

ounces (mass) 0.02834952 kilograms

ounces (US fluid) 2.957353 E-05 cubic meters

pounds (mass) 0.45359237 kilograms

quarts (US liquid) 9.463529 E-04 cubic meters

square feet 0.09290304 square meters

square miles 2.589998 E+06 square meters

square yards 0.8361274 square meters

tons (2,000 pounds, mass) 907.1847 kilograms

tons (2,000 pounds, mass) per square foot 9,764.856 kilograms per square meter

yards 0.9144 meters
ERDC/CHL TR-20-15 48

Acronyms and Abbreviations

CS construction sand 

DQM Dredging Quality Management 

FS fine sand 

MRE mean relative error

PVC polyvinyl chloride

RE relative error

SEM standard error of the mean 

TSHD trailing suction hopper dredges 

VS Vicksburg silt 

SAND Sediment Assessment and Needs Determination 

SD standard deviation 
REPORT DOCUMENTATION PAGE Form Approved

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1. REPORT DATE 

August 2020

2. REPORT TYPE

Final Report

3. DATES COVERED (From - To)

4. TITLE AND SUBTITLE

Sediment Sorting by Hopper Dredging and Pump-Out Operations: Sampling Methods and 

Analysis

5a. CONTRACT NUMBER

5b. GRANT NUMBER

5c. PROGRAM ELEMENT NUMBER

110

6. AUTHOR(S)

Duncan B. Bryant, Anthony M. Priestas, S. Jarrell Smith, and Katherine E. Brutsché

5d. PROJECT NUMBER

484149

5e. TASK NUMBER

A1040

5f. WORK UNIT NUMBER

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)

Coastal and Hydraulics Laboratory

US Army Engineer Research and Development Center

3909 Halls Ferry Road

Vicksburg, MS 39180-6199

8. PERFORMING

ORGANIZATION REPORT

NUMBER

ERDC/CHL TR-20-15

9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) (see reverse) 10. SPONSOR/MONITOR'S ACRONYM(S)

USACE, USDOI BOEM, SAJ

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Approved for public release; distribution is unlimited.

13. SUPPLEMENTARY NOTES

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14. ABSTRACT

Hopper dredging operations for beach and nearshore placement typically include periods of overflow, which produces some degree of 

separation between the size fractions of the dredged sediment. The degree of separation and the controlling factors are presently poorly 

known. This report focuses on laboratory experiments aimed at determining (1) suitable sampling methods on a dredge, (2) composite 

sampling techniques to reduce analysis cost, (3) associated sampling intervals to achieve suitable sediment representation of a hopper 

load, and (4) a hydraulic means of sample splitting. Results showed that no statistical difference exists among the three methods used to 

sample the hopper weir overflow. The method used to sample deposited hopper sediment identified a bias in the percent fines that 

resulted from flow sheltering. Further, it was found that composited samples were able to quantify the concentration and percent fines 

accurately, although an analytical data experiment showed that the accuracy of a composited sample is dependent on the sampling 

intervals. The accuracy of the fines and concentration from a hydraulic sample splitter was found to be dependent on median grain size, 

with fine sediment being evenly distributed and coarser sediment increasing the error in concentration and grain size distribution.

15. SUBJECT TERMS 

Dredges, Dredging, Lake sediments, Marine sediments, Particle size determination—Sampling, River sediments, Sedimentation analysis

16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF 

ABSTRACT

SAR

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OF 

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59

19a. NAME OF RESPONSIBLE PERSON

Duncan B. Bryant a. REPORT

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601-634-3898

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Prescribed by ANSI Std. Z39.18
9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES)) (continued)

US Army Corps of Engineers, Headquarters

Washington, DC 20314-1000

US Department of the Interior, Bureau of Ocean Energy Management

Washington, DC 20240

US Army Corps of Engineers, Jacksonville District

Jacksonville, FL 32207-8175