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DRAFT

Sedflume Consolidation Analysis

Passaic River, New Jersey

Prepared for:

Hydroqual, Inc.

and

U.S. Environmental Protection Agency

Prepared by:

Sea Engineering, Inc.

200 Washington Street, Suite 210

Santa Cruz, CA 95060

Tel: (831) 421-0871

Fax: (831) 421-0875

DRAFT Sedflume Consolidation Report



1

Executive Summary Sea Engineering, Inc. (SEI) conducted a Sedflume analysis on four consolidation cores

created from sediment at Passaic River Site, New Jersey. The primary goal of this work

was to characterize the consolidation characteristics of sediment at the Passaic River Site.

The Sedflume analysis determines sediment erosion rates, critical shear stress, particle

size and bulk density. The following is a brief description of the four consolidation

cores.

• Core P1D was a 1 day consolidation core. The core consisted of fluidic gray silt

surface layer over gray silt. Very fine organic material (including leaves, small

sticks and shells) was observed at the surface and throughout core. Mean grain

size is 22.42 µm (silt).

• Core P7D was a 7 day consolidation core. The core consisted gray silt. Very fine

organic material (including leaves, small sticks and shells) were present at the

surface. Organic material was observed down core. Mean grain size was 23.22

µm (silt).

• Core P17D was a 17 day consolidation core. The core consisted of layer of light

gray silt, over gray silt with pockets of black sediment. Very fine material

(including leaves, roots, small sticks and shells) was observed at the surface and

throughout core. Gas bubbles were also observed down core. At 5 cm an anoxic

decay odor was detected that remained down core. The mean grain size was

24.09 µm (silt).

• Core P28D was a 28 day consolidation core. The core consisted of consisted of a

layer of light gray silt over gray silt with pockets of black sediment. Very fine

organic material (including leaves, small sticks, and shells) was observed at the

surface and throughout core. Gas bubbles were also observed down core. At 5

cm an anoxic decay odor was detected that remained down core. The mean grain

size was 25.22 µm (silt).




2

Introduction

Sea Engineering, Inc. (SEI) conducted a Sedflume analysis for HydroQual on four

consolidation cores created from sediment at Passaic River Site, New Jersey. The

primary goal of this work was to characterize the consolidation characteristics of

sediment at the Passaic River Site. Surface sediment was collected at a location that has

been identified as depositional for fine material in the Lower Passaic River (LPR). The

material was mixed together (i.e. composited) and reconstructed into four laboratory

Sedflume cores. The four reconstructed cores will be evaluated to determine the effects

of consolidation on erosion rates and sediment density over time. A core from the batch

was tested in the Sedflume at 1-day, 7-days, 17-days, and 28-days to determine the

effects of consolidation on the stored sediments. The Sedflume analysis determines

sediment erosion rates, critical shear stress, particle size and bulk density. In addition,

each core was sub-sampled at vertical intervals to determine sediment bulk density and

particle size distribution. Critical shear stresses were determined through two

interpolation techniques for each vertical interval sampled. The following report outlines

the procedures used in the Sedflume analysis, presents the Sedflume data, and provides a

description of the results.

Experimental Procedures

A detailed description of Sedflume and its application are given in McNeil et al (1996)

and Roberts et al (1998). The following section provides a general description of the

Sedflume analysis conducted for this study.

Description of Sedflume

Sedflume is shown in Figure 1 and is essentially a straight flume that has a test section

with an open bottom through which a rectangular cross-section core containing sediment

can be inserted. The main components of the flume are the core; the test section; an inlet

section for uniform, fully-developed, turbulent flow; a flow exit section; a water storage

tank; and a pump to force water through the system. The coring tube, test section, inlet

section, and exit section are made of clear acrylic so that the sediment-water interactions

can be observed. The coring barrel has a rectangular cross-section, 10 cm by 15 cm, and

can be up to 1 m in length.




3

Figure 1. Sedflume Diagram

Water is pumped through the system from a 300 gallon storage tank, through a 5 cm

diameter pipe, and then through a flow converter into the rectangular duct shown. This

duct is 2 cm in height, 10 cm in width, and 120 cm in length; it connects to the test

section, which has the same cross-sectional area and is 15 cm long. The flow converter

changes the shape of the cross-section from circular to the rectangular duct shape while

maintaining a constant cross-sectional area. A ball valve regulates the flow so that the

flow into the duct can be carefully controlled. Also, there is a small valve in the duct

immediately downstream from the test section that is opened at higher flow rates to keep

the pressure in the duct and over the test section at atmospheric conditions.

At the start of each test the core and the sediment it contains are then inserted into the

bottom of the test section. An operator moves the sediment upward using a piston that is

inside the core and is connected to a hydraulic jack with a 1 m drive stroke. The jack is

driven by the release of pressure that is regulated with a switch and valve system. By this

means, the sediments can be raised and made level with the bottom of the test section.

The speed of the hydraulic jack movement can be controlled at a variable rate in

measurable increments as small as 0.5 mm.




4

Water is forced through the duct and the test section over the surface of the sediments.

The shear produced by this flow causes the sediments to erode. As the sediments in the

core erode, they are continually moved upward by the operator so that the sediment-water

interface remains level with the bottom of the test and inlet sections. The erosion rate is

recorded as the upward movement of the sediments in the coring tube over time.

Sedflume Core Preparation

In situ sediment collection was done by Malcolm Pirnie, Inc. Fifteen gallons of

sediment were collected from the top 15 cm of the sediment bed. These sediments were

shipped in buckets to the SEI Santa Cruz, Ca laboratory. The sediments were composited

with water in the SEI laboratory and poured into 4 prepared core barrels. Sediment cores

of 40 - 50 cm in length were reconstructed by this method. Cores were immediately

visually inspected for length and quality. Approved cores were capped and stored in the

laboratory for 1, 7, 17, or 28 days depending on the test to be performed on that core. Dr.

Craig Jones was responsible for corrective action regarding sample method requirements.

All physical bulk properties for each sediment mixture remain constant except for bulk

density. Particle size was sampled in each core to ensure no significant variation among

cores. Bulk density as a function of depth was measured periodically during the test and

cores were tested in the Sedflume for erosion rates over a range of shear stresses.

Measurements of Sediment Erosion Rates

The procedure for measuring the erosion rates of the sediments as a function of shear

stress and depth were as follows. The sediment core was inserted into the Sedflume test

section using the hydraulic jack until the sediment surface was even with the bottom of

the Sedflume channel. A measurement was made of the core length. The flume was then

run at a specific flow rate corresponding to a particular shear stress (McNeil et al., 1996).

Erosion rates are obtained by measuring the core length at different time intervals, taking

the difference between each successive measurement, and dividing by the time interval as

shown in Equation 1:

T

zE

∆= (1)

E = Erosion rate

∆z = Amount of sediment eroded

T = Time

In order to measure erosion rates at several different shear stresses using only one core,

the following procedure was used. Starting at a low shear stress, the flume was run

sequentially at higher shear stresses with each succeeding shear stress being twice the

previous one. Generally about four shear stresses are run sequentially. Each shear stress

was run until at least 1 to 2 mm but no more than 2 cm were eroded for that shear stress.

The time interval was recorded for each run with a stopwatch. The flow was then

increased to the next shear stress, and so on until the highest shear stress was run. This

cycle was repeated until all of the sediment had eroded from the core. If after three

cycles a particular shear stress showed a rate of erosion less than 10-4

cm/s, it was




5

dropped from the cycle; if after many cycles the erosion rates decreased significantly, a

higher shear stress was included in the cycle.

Determination of Critical Shear Stress

The critical shear stress of a sediment bed, τcr, is defined quantitatively as the shear stress

at which a very small, but accurately measurable, rate of erosion occurs. For Sedflume

studies, this rate of erosion has been practically defined as 10-4

cm/s. This represents 1

mm of erosion in approximately 15 minutes. Since it is difficult to measure τcr exactly at

10-4

cm/s, erosion rates were determined above and below 10-4

cm/s. The τcr was then

determined by two interpolation techniques, linear and power law regression (McNeil et

al. 1996; Roberts et al., 1998).

Measurement of Sediment Bulk Properties

In addition to erosion rate measurements, samples were collected to determine the water

content, bulk density, and particle size of the sediments. Sub-samples were collected

from the surface of the Sedflume cores at the end of each erosion cycle. This allowed 5

samples to be collected approximately every 5 cm for analysis.

Bulk density was determined in the SEI Sedflume laboratory by water content analysis

using methods outlined in Hakanson and Jansson (2002). This consisted of determining

the wet and dry weight of the collected sample to determine the water content, W, from

Equation 2.

w

dw

M

MMW

−= (2)

W = water content

Mw = wet weight of sample

Md = dry weight of sample

Once the water content was calculated, the bulk density, ρb, was determined from

Equation 3.

Wwsw

sw

b)( ρρρ

ρρρ

−+= (3)

ρw = density of water (1 g/cm3)

ρs = density of sediment particle (2.65 g/cm3)

Particle size distributions were determined using laser diffraction analysis. Samples

collected from the Sedflume core were prepared and inserted into a Beckman Coulter LS

13 320. Each sample was analyzed in three 1-minute intervals and the results of the four

analyses were averaged. This method is valid for particle sizes between 0.04 and 2000

µm. Any fraction over 2000 µm was weighed and compared to total sample weight to

determine the weight percentage greater than 2000 µm. During the analysis no

significant fraction over 2000 µm was sampled.




6

Table 1 summarizes all measurements conducted during the Sedflume analysis.

Table 1. Parameters measured and computed for the Passaic River Site.

Measurement Definition Units Detection Limit Bulk Density, ρb

(wet/dry weight) W

wsw

sw

b)( ρρρ

ρρρ

−+=

g/cm3

Same as water

content

Water Content

w

dw

M

MMW

−=

unit less 0.1g in sample

weight ranging from

10 to 50 g

Particle Size

Distribution

Distribution of particle sizes by

volume percentage using laser

diffraction

µm 0.04 µm – 2000 µm

Erosion Rate E = ∆z/T cm/s ∆z > 0.5mm

T > 15s

Critical Shear Stress

τcr

Shear stress when erosion rate

equals 10-4

cm/s

N/m2 0 to 10.0 N/m

2

This value is

interpolated as

described in the text.

W = water content

Mw = wet weight of sample

Md = dry weight of sample

∆z = amount of sediment eroded

T = time

ρw = density of water (1 g/cm3)

ρs = density of sediment (2.65 g/cm3)




7

Summary Sea Engineering, Inc. (SEI) conducted a Sedflume analysis on four consolidation cores

created from sediment at Passaic River Site, New Jersey. The primary goal of this work

was to characterize the consolidation characteristics of sediment at the Passaic River Site.

The Sedflume analysis determines sediment erosion rates, critical shear stress, particle

size and bulk density. The following is a brief description of the four consolidation

cores.

• Core P1D was a 1 day consolidation core. The core consisted of fluidic gray silt

surface layer over gray silt. Very fine organic material (including leaves, small

sticks and shells) was observed at the surface and throughout core. Mean grain

size is 22.42 µm (silt).

• Core P7D was a 7 day consolidation core. The core consisted gray silt. Very fine

organic material (including leaves, small sticks and shells) were present at the

surface. Organic material was observed down core. Mean grain size was 23.22

µm (silt).

• Core P17D was a 17 day consolidation core. The core consisted of layer of light

gray silt, over gray silt with pockets of black sediment. Very fine material

(including leaves, roots, small sticks and shells) was observed at the surface and

throughout core. Gas bubbles were also observed down core. At 5 cm an anoxic

decay odor was detected that remained down core. The mean grain size was

24.09 µm (silt).

• Core P28D was a 28 day consolidation core. The core consisted of consisted of a

layer of light gray silt over gray silt with pockets of black sediment. Very fine

organic material (including leaves, small sticks, and shells) was observed at the

surface and throughout core. Gas bubbles were also observed down core. At 5

cm an anoxic decay odor was detected that remained down core. The mean grain

size was 25.22 µm (silt).

A comparison of critical shear stress (Figure 18) and bulk density (Figure 19) with depth

of the four consolidated cores evaluated from sediment at the Passaic River Site, New

Jersey.




8

Figure2. Critical shear stress with depth comparison of four consolidation cores.

Figure 3. Bulk density with depth comparison of four consolidation cores.




9

References

Hakanson, L., and M. Jansson, 2002, Principles of Lake Sedimentology. Blackburn Press,

Caldwell, New Jersey, USA.

Jepsen, R., J. Roberts, and W. Lick, 1997, Effects of bulk density on sediment erosion

rates, Water, Air and Soil Pollution, 99:21-31.

McNeil, J., C. Taylor, and W. Lick, 1996, Measurements of erosion of undisturbed

bottom sediments with depth, J. Hydr. Engr., 122(6):316-324.

Roberts, J., R. Jepsen, D. Gotthard, and W. Lick, 1998, Effects of particle size and

bulk density on erosion of quartz particles, J. Hydr. Engrg., 124(12):1261

1267.




10

Appendix A – Particle Size Distributions

Beckman Coulter LS Particle Size Analyzer

Passaic River Consolidation Core16 Dec 2008

File name: C:\Documents and Settings\Lisa\My Documents\Projects\ConsolidationPassaic_Sedflume\ConsolidationPassaic_ParticleSize\P1D-1__720.$avP1D-1__720.$av

File ID: P1D-1Operator: IsraelComment 2: SampleOptical model: Fraunhofer.rf780zLS 13 320 SW Aqueous Liquid Module

Run length: 60 secondsPump speed: 80Average of 3 files:C:\LS13320\Projects\ConsolidationPassaic\P1D-1__718.$lsC:\LS13320\Projects\ConsolidationPassaic\P1D-1__719.$lsC:\LS13320\Projects\ConsolidationPassaic\P1D-1__720.$ls

Volume Statistics (Arithmetic) P1D-1__720.$av

Calculations from 0.375 µm to 2000 µm

Volume: 100%Mean: 70.96 µmMedian: 22.92 µmMean/Median ratio: 3.096Mode: 34.59 µm

S.D.: 129.6 µmVariance: 16803 µm2

C.V.: 183%Skewness: 3.420 Right skewedKurtosis: 13.34 Leptokurtic

<10%3.099 µm

<25%8.125 µm

<50%22.92 µm

<75%66.38 µm

<90%179.0 µm

Differential Volume (Average) (2 S.D.)

2000100060040020010060402010864210.60.4Particle Diameter (µm)

3

2.5

2

1.5

1

0.5

0

Vol

ume

(%)











<10%2.956 µm

<25%7.684 µm

<50%21.92 µm

<75%65.23 µm

<90%170.1 µm



3

2.5

2

1.5

1

0.5

0

Vol

ume

(%)











<10%3.232 µm

<25%8.825 µm

<50%24.77 µm

<75%65.49 µm

<90%153.1 µm



3

2.5

2

1.5

1

0.5

0

Vol

ume

(%)











<10%2.842 µm

<25%7.450 µm

<50%21.67 µm

<75%67.80 µm

<90%174.8 µm



2.5

2

1.5

1

0.5

0

Vol

ume

(%)



File name: C:\Documents and Settings\Lisa\My Documents\Projects\ConsolidationPassaic_Sedflume\ConsolidationPassaic_ParticleSize\P17-5__747.$avP17-5__747.$av

File ID: P17-5Operator: IsraelComment 2: SampleOptical model: Fraunhofer.rf780zLS 13 320 SW Aqueous Liquid Module

Run length: 60 secondsPump speed: 80Average of 3 files:C:\LS13320\Projects\ConsolidationPassaic\P17-5__745.$lsC:\LS13320\Projects\ConsolidationPassaic\P17-5__746.$lsC:\LS13320\Projects\ConsolidationPassaic\P17-5__747.$ls

Volume Statistics (Arithmetic) P17-5__747.$av





<10%3.004 µm

<25%7.834 µm

<50%26.83 µm

<75%103.3 µm

<90%314.0 µm



2.5

2

1.5

1

0.5

0

Vol

ume

(%)











<10%2.525 µm

<25%6.489 µm

<50%21.35 µm

<75%73.34 µm

<90%174.7 µm



2.5

2

1.5

1

0.5

0

Vol

ume

(%)




File ID: P28D-1Operator: ANDESComment 2: SampleOptical model: Fraunhofer.rf780zLS 13 320 SW Aqueous Liquid Module







<10%2.745 µm

<25%6.974 µm

<50%22.09 µm

<75%76.06 µm

<90%177.6 µm



2.5

2

1.5

1

0.5

0

Vol

ume

(%)




File ID: P28D-5Operator: ANDESComment 2: SampleOptical model: Fraunhofer.rf780zLS 13 320 SW Aqueous Liquid Module







<10%3.595 µm

<25%9.023 µm

<50%28.36 µm

<75%97.55 µm

<90%250.6 µm



2.5

2

1.5

1

0.5

0

Vol

ume

(%)