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US Army Corps

of Engineers

Water Resources

Support Center

! Management of Bottom Sediments

. Containing Toxic Substances

Proceedings of the 8th U. S./Japan

O Experts Meeting

8-10 November 1982 -

Tokyo, Japan

Thomas R. Patin. Editor

; .. • | i -• •: ,• . 1 , , . J3> .

C July 1984

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REPORT DOCMAENTATION PAGE BEFOREJ COMIPLETING F~ORMI 4 ri r~f -1 ý-bff~ rvoE op mEpoo a pEplrno CovERIEO

VANAGýYAENT UF BOTTOM SEDIM4ENTS CONTAINiING TOXIC Fnlrpr - ~~~SUBSTANCFS: PRO~CEEDINGS OF THE STH.U. S./JAPAN Fzirpr

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PREFACE

The 8th U. S./Japan Meeting on Management of Bo.tou Sediments Containing

Toxic Substances was held 8-10 November 1982 in Tokyo. japan. The meeting is

held annually through an agreement with the U. S. Army Corps of Engineers and

thie Japan Ministry of Transport to provide a forum for presentation of papers

and in-depth discussions on dredging and disposal of contaminated sediment.

COL Maximilian Imhoff, Commander and Director of the Water Resources

Support Center (WRSC) at the time of. the meeting, was the U. S. Chairman.

Mr. Yasuo Okada, Ministry of Transport, Tokyo, Japan, was the Japanese

Chairman.

Coordinator of the organizational activities and editor of this

report was Mr. Thomas R. Patin, program assistant, Dredging Operations

Technical Support Program (DOTS), U. S. Army Engineer Waterways Experiment

Station, Vicksburg. Miss. Mr. Charles C. Calhoun, Jr., was Program Manager,

DOTS. At the time of publication of this report,' COL George R. Kleb was

Commander of WRSC.

1/

' L'. 
CONTENTS

Page

PREFACE ............................. .............................. 1

ATTENDEES ............................ ............................. 4

AGENDA . ... .......................... ............................ 5

JOINT COMMUNIQUE . . . ..................... ....................... 9

PUBLIC WORKS AIMING AT IMPROVEMENT OF PORT AND MARINE ENVIRONMENT IN JAPAN by Y. Okada ................... .................... 10

REMOVAL OF BOTTOM SEDIMENTS IN OSAKA PORT BY THE PNEUMA PUMP

DREDGE "SHUNKAI" by S. Kasajima .......... ................. .. 16

CONSTRUCTIVE USE OF DREDGED SAND by N. E. Parker .. ......... 40

RECLAMATION WITH SOFT SEA BOTTOM SEDIMENTS by Y. Shiratori

and H. Kato .................... ........................... .. 52

CAPPING OF DREDGED MATERIAL DISPOSAL MANAGEMENT FOR NEW YORK

HARBOR by J. M. Mansky ............. ..................... .. 78

RESTORATION STUDY OF DREDGING IN LAKE KASUMIGAURA by F. Kodama

and T. Fukushima ................. ........................ 94

BOUNDARY CONDITIONS OF SEDIMENT SURFACES VIEWED FROM DO

BEHAVIOR by T. Yoshida and T. Mimaki ....... ............. . 112

FIELD VERIFfCATION OF TESTING AND PREDICTIVE METHODOLOGIES FOR

EVALUATING DREDGED MATERIAL DISPOSAL ALTERNATIVES

by R. Peddicord .................. ......................... .. 130

STUDIES ON ANALYTICAL METHOD OF ACRYLAMIDE MONOMER AND

ACCUMULATION INTO FISH by M. Fujiki, J. Asada,

and T. Shimizu ................... ......................... 147

SPECIFICATIONS OF A MODEL OCEAN DISPOSAL SITE FOR DREDGED MATERIAL

by W. Pequegnat .................. ........................ . 167

SIMULATION OF ESTUARINE SILT TRANSPORT ACCORDING TO STORM WATER

RUNOFF by Y. Saba ................ ........................ 185

RESCUING THE PORTS - AN UPDATE by H. Haar .... ............. .. 202

SOIL IMPROVEMENT BY DEEP CEMENT CONTINUOUS MIXING METHOD AND ITS

EFFECT ON THE ENVIRONMENT by T. Otsuki and M. Shima ....... 215

A COMPARISON OF METHODS FOR ESTIMATING NUTRIENT RELEASE FROM

LAKE SEDIMENTS by M. Hosomi, M. Okada, and R. Sudo ....... 238

DREDGING AND MANAGEMENT PROBLEMS IN LAKE SUWA

by K. Nikaido and M. Akabane ........... .................. 251

EMERGENCY RESPONSE EQUIPMENT TO CLEAN UP HAZARDOUS CHEMICAL

RELEASES AT SPILLS AND UNCONTROLLED WASTE SITES

by I. Wilder ................... .......................... 262

LEGAL RESTRICTIONS AND PRESENT CONDITION OF DREDGED MATFr.lAL

DISPOSAL IN JAPAN by A. Sugiyama ......... ................ 281

2
Page

ECO-KI1 ETIC MODEL FOR THE ACCbMULATION OF PCB IN MARINE FISHES

by J, O'Connor and J. Pizza ............ .................... .. 285

ASPECT! OF THE DAMOS MONITORING PROGRAM IN THE NEW ENGLAND

REGI N by A. Andreliunas ............. ..................... .. 304

AN OVE VIEW OF A DREDGING DEMONSTRATION IN CONTAMINATED MATERIAL,

JAMEJ RIVER, VIRGINIA by R. E. Hudson and R. G. Vann ....... .. 312

FIELD DREDGING TEST OF SOFT MUD LAYER BY A FRONT-OPEN TIYPE DRAG

HEAD by Y. Irie .................. ........................... .. 326

OVERVIEW OF CORPS RESEARCH PROGRAM ON DREDGING CONTAMINATED

SEDIMENTS by R. Montgomery ............. .................... 381

BOTTOM SEDIMENT DREDGE "CLEAN-UP" - PRINCIPLE AND RESULTS

by E Sato ..................... ............................ 403

PERFORMANCE TESTS OF PNEUMA DREDGE PUMP by T. W. Richardson ..... 419

SEDIMENT RESUSPENSION IN THE VICINITY OF THE CUTTER HEAD

by H. Koba and T. Shiba .............. ...................... .. 434

THE LONG-TERM EFFECTS OF DREDGING OPERATIONS PROGRAM

by T. R. Patin, T. L. Hart, and C. C. Calhoun ... ........... .. 442

SPECIALIZED DREDGES DESIGNED FOR BOTTOM SEDIMENT DREDGING

by A. Kaneko, Y. Watari, and N. Aritomi ...... .............. .. 450

3
a..

ATTENDEES

8th ANNUAL MEETING

U. S./JAFAN EXPERTS MEETING

U. S. Delegation

COL Maximilian Imhoff, Cochairman CE, Commander and Director, Water Resources Support

Center (WRSC)

R. Murden SWilliam CE, Chief, Dredging Division, WRSC

Neill E. Parker CE, Coastal Engineering Research Center

Jim M. Mansky CE, New York District

Richard K. Peddicord CE, Waterways Experiment Station

Willis Pequegnat Tereco Corporation

Herbert R. Haar Board of Commissioners, Port of New Orleans

I. Wilder U. S. Environmental Protection Agency

J. O'Connor New York State University Medical Center

Vito Andreliunas CE, New England Division

Ron VAnn CE, Norfolk District

Raymond L. Montgomery CE, Waterways Experiment Station ".

Japanese Delegation

Yasuo Okada, Cochairman Bureau of Ports and Harbours, Ministry of Transport

(MOT)

S. Kasajima Port and Harbour Bureau, City of Osaka

Y. Shiratori Port and Harbour Research Institute, MOT

F. Kodama Kasumigaura Work Office, Ministry of Construction

(MOC)

Tatsuo Yoshida Bottom Sediment Management Association

Motoo Fujiki University of Tsukuba L

Y. Baba Public Works Research Institute, MOC

Tadashi Otsuki Dredging and Reclamation Engineering Association

M. Hosomi Environmental Agency

K. Nikaido Nagoya Prefecture Government

A. Sugiyama Ports and Harbour Bureau, MOT

Y. Irie 2nd District Port Construction Bureau

E. Sato Japan Dredging and Reclamation Engineering

Association

Hiromi Koba Japan Dredging and Reclamation Engineering

Association

A. Kanekc Japan Dredging and Reclamation Engineerijng

Association

4q
AGENDA

8th U.S./JAPAN EXPERTS MEETING ON MANAGEMENT

OF BOTTOM SEDIMENTS CONTAINING

TOXIC SUBSTANCES

Tokyo, Japan

8-10 November 1982

Cochairmen

Mr. Yasuo Okada

Director, Environmental Protection Division

Bureau of Ports and Harbours, Ministry of Transport

COL Maximilian Imhoff

U. S. Army Corps of Engineers, Water Resources Support Center

Monday, November 8, 1982

1000-1030 Opening session

1030-1100 Y. Okada, "Public Works Aiming at Improvement of Port and

Marine Environment in Japan," Ports and Harbours Bureau,

Ministry of Transport, Japan

1100-1130 S. Kasajima, "Removal of Bottom Sediments in Osaka Port by the

Pneuma Pump Dredge 'SHUNKAI,'" Port and Harbour Bureau, City

of Osaka, Japan

1130-1200 N. E. Parker, "Constructive Use of Dredged Sand," Coastal Engineering Research Center, Corps of Engineers, USA

1200-1330 Luncheon

1330-1400 Y. Shiratori and H. Kato, "Reclamation with Soft Sea Bottom

Sediments," Port and Harbour Research Institute, Ministry of

Transport, Japan

5

_4
I

1400-1430 J. M. Mansky, "Capping of Dredged Material Disposal Management

for New York Harbor," U. S. Army Engineer District, Now York,

Regulatory Branch, USA

1430-1500 F. Kodama and T. Fukushima, "Restoration Study of Dredging in

Lake Kasumigaura," Kasumigaura Work Office, Ministry of Construction, Japan

1500-1530 Break

1530-1600 T. Yoshida and T. Mimaki, "Boundary Conditions of Sediment

Surfaces Viewed from DO Behavior," Japan Bottom Sediment

Management Association, Izumo Construction Work Bureau, Ministry of Construction, Japan

1600-1630 R. Peddicord, "Field Verification of Testing and Predictive

Methodologies for Evaluating Dredged Material Disposal Alternatives," Waterways Experiment Station, Corps of Engineers,

USA

1630-1700 M. Fujiki, J, Asada, and T. Shimizu, "Studies on Analytical

Method of Acrylamide Monomer and Accumulation into Fish,"

Institute of Community Medicine, University of Tsukuba,

Japan

1700-1730 W, Pequegnat, "`pecifications of a Model Ocean Disposal Site

for Dredged Material," TerEco Corporation, College Station,

Texes, tUSA

1800-2000 Reception for U. S. delegation

Tuesday, November 9, 1982 .4

1000-1030 Y. Baba, "Simulation of Estuarine Silt Transport According to

Storm Water Runoff," Public Works Research Institute, Ministry of Construction, Japan

1030-1100 H. Haar, "Rescuing the Ports - An Update," Port of New Orleans,

Louisiana, USA

1100-1130 T. Otsuki and M. Shima, "Soil Improvement by Deep Cement Continuous Mixing Method and Its Effect on the Environment,"

Japan Dredging and Reclamation Engineering Association,

Japan

1130-1200 M. Hosomi, M. Okada, and R. Sudo, "A Comparison of Methods for

Estimating Nutrient Release from Lake Sediments," National

Institute for Environmental Studies, Environmental Agency,

Japan

1200-1330 Luncheon -1

*6
'f.I

*,6m

1330-1400 Film "Lakes and Sediment"

1400-1430 K. Nikaido and M. Akabane, "Dredging and Management Problems .

in Lake Suwa," Japan Bottom Sediment Management Association,

Suwa Construction Work Office, Nagoya Prefecture Government, 6

Japan

1430-1500 I. Wilder, "Emergency Response Equipment to Clean up Hazardous

Chemical Releases at Spills and Uncontrolled Waste Sites,""

Municipal Environmental Research Laboratory, U. S. Environmental Protection Agency, USA

1500-1530 Break

1530-1600 A. Sugiyama, "Legal Restrictions and Present Condition of

Dredged Material Disposal in Japan," Ports and Harbours

Bureau, Ministry of Transportation, Japan

1600-1630 J. O'Connor and J. Pizza, "Eco-Kinetic Model for the Accumuiation of PCB in Marine Fishes," New York'State University

Medical Center, USA

1630-1700 A. Andreliunas, "Aspects of the DAMOS Monitorin6 Program in -

the New England Region," New England Division, Corps of

Engineers, USA

Wednesday, November 10, 1982 61

1000-1030 R. E. Hudson and K. G. Vann, "An Overview of a Dredging Demonstration in Contaminated Material, James River, Virginia,"

Department of the Army, Corps of Engineers, Norfolk

District, USA

1030-1100 Y. Irie, "Field Dredging Test of Soft Mud Layer by a FrontOpen Type Drag Head," the 2nd District Port Construction.

Bureau, Ministry of Transportation, Japan

1100-1130 R. Montgomery, "Overview of Corps Research Program on Dredging

Contaminated Sediments," Waterways Ez:oeriment Station, Corps

of Engineers, USA

1130-1200 E. Sato, "Bottom Sediment Dredge "CLEAN-UP" -Principle and

Results," Japan Dredging and Reclamation Engineering Association, Japan

1200-1330 Luncheon _7

1330-1400 Film "CLEAN-UP"

1400-1430 T. W. Richardson, "Perfor'ance Tests of Pneuma Dredge Pump,"

Waterways Experiment Station, Corps of Engineers, USA S

7 0::
-o

1430-1500 H. Koba and T. Shiba, "Sediment Resuspension in the Vicirity

of the Cutter Head," Japan Dredging and Reclamation Engineering Association, Japan

11500-1530 Break

1530-1600 T. R. Patin, T. Hart, and C. C. Calhoun, "The Long-Term

Effects of Dr,. ng Operations Program," Waterways Experiment Station, C, ps of Engineers, USA

1600-1630 A. Kaneko, Y. Watari, and N. Aritoml, "Specialized Dredges

Designed for Bortom Sediment Dredging," Japan Dredging and

Reclamation Engineering Association, Japan

1630-1700 Discussion

S1700-1730 Closing session

SCosn

I

oS
JOINT COKMIUN I'E

The 8th U.S./Japan Experts Meeting otn Yanagement of Bottomr .editrents

Containing Toxic Substances %am held by the United Statc. (Cýloe1l Maxi'itiiarV

Imhoff, Commander/Director, Water Resources Support Certer, ..S. Army Corps of

Engineers) ard the Japanese (Yasuo Okada, Director, Enviror-ýentdl Protection

Division, Ports and Harbours 3urea'l. .Ministry of Transport) Co-chaiirsmer

Nov. 8-10, 1982, at Tokyo, Japan. The purpose of the conferetic. was to

exchange information in both regulatory and technica! *reaas relevant to hcttcom

sediment management and to explore are;:s where joint effort* wotuld be

fruitful.

The United States and Japanese experts presented papers on several technical and managerial subjecth, including: public works aimitng it improvement

of port and marine environment In Japan; dredging works in Osak.i Port,

Lake Kasumigaura, Lake Suwa, and the James River; experiments and studies for

physical and chemical characteristics of bottom sediment; stud,es on toxic.

materLals accumulated in organisms; legal restrictions, present condition', and

new methods for dredged material dliqptftal: advances in aredging technology

including new equipment and operationil techniques (Drag head, (C)*an-up.

Pneuma pump and Refresher); dredging technologies and meth(Aq_ for dredged

material disposal with due regard to the environrental impAct; And *ergency

response equipment to clean up hazardous chemical release.

The tnited States and Japanese attendeo rtonsxited prL-nlrilv of engineers, blologl.st", and chemists fron admintistratlve agercle1., tiniversittes,

port authorities, and related aspociation-' of enginepring o.ipaili.*. There

w4s general agreement that this conference was highly *uccesuul In meeting

its majer goal: to exchange the most recent inltorrati.o , n minaoeient techn'.quer and the environmeital effects of qedime•.r. cortaining toxics and other

poI 1 t.an ts. Consistent with the prvy lti A ,,' the me-•mrandtaw o u derstrindng, the nevt meeting will he 1,vld tv ti,• 'ilted vt.iteo And t 0t dite

wl!1 lie decided jointly bv the Co-chairmen.

DiPrector, Fnvironmert al (,m.'umrer/Dflr. tor.r 'W.ter %.ur ,ets

1'r.,r,,r ion D)ivis on, Stpp-,rt ( enter, I Armv .*rp%,,

i''r! ~ anoj t;i rho, rq F ureau , tit Fivr i tervo

ini trv of Trarspc'rt

i ".,"A..r i'. ., • ' ' k 

_ _ _ _ _ _ _ _ _ __ _ _ _ 

Je...
6

• PUBLIC WORKS AIMING AT IMPROVEMENT OF PORT AND

MARINE ENVIRONMENT IN JAPAN

Yasuo Okada

Director, Environmental Protectiot, Division

Bureau of Ports and Harbors, Ministry of Transport

INTRODUCTION

Port and marine environment improvement works in Japan are carried out

as a part of port improvement works.

Port improvement works are systematically carried out by formulating a

j Five-Year Plan for Port Improvement under the Law for Emergency Measures of

Port Improvement.

The current Five-Year Plan for Port Improvement is the sixth plan and

covers the period from fiscal 1981 to 1985 with a total investment of

V4,260 billion. This plan lists "promotion of works aimed at the realization

of pleasant port and marine environment" as one of its important tasks. The

plan is thus intended to step up the improvement of port and marine environment by allocating about 1/10 of the total investment to it.

These works include marine environment improvement works and studies for

naterialization of port works conducted by government directly, works to provide faciliries for preventing oil pollution of seawater, and port pollution

prevention works and port environment iml-rovement works conducted by a port

management body with government subsidies Table 1 shows the trends of the

expenditure for port and marine environment improvement works.

MARINF FNVIRONMENT IMPROVEMENT '^'ORKS

1hese works are Intended to prevent marine pollution and to conserve the

marine environment. In particular, accumulation work for floating r-fuse and

oil has been carried out in badly polluted waters outside port and fishing

port areas since 1974 as government-executed works.

Cleaning, work for floating refuse and oil is scheduled to be carried out

in 1982 vi in thv provious year in three areas of Tokyo Bay, Ise Bav, and the

Seto Inland Sea.

1he fleet for -iarine onvironment im;rovement work now comprises 16 ships

• it h i newlv constrtictd co-ibined-use ship both for refuse knd oil. I"he

.;'%tcm of chlin iri. rutu-.e and oil floating in inland seas and bays has now

been r"::b 1, c or~;leted ( !c Vable 2).

10
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STUDIES FOR MATkERIALIZATION OF PORT WORKS

These studies are conducted prior to the commencement of actual -.york

to ascertain their economic and technical feasibilities. Diirin-. th'e corrent

fiscal vear, a bottom sediment clarif icat ion plan is schedule'd tor Vokvo Bav,

Ise Ba:, and the Seto Inland Sea. An interprerecture waste d i.spos.il site in

* Tokyo Bay is also projected.

hefo)rmer was explained at the 7th US/.Iapain meet ing_ 'eLitri

designed to cinstruct a Waste disposal site at sea because it has; become

*inc reas inlv '!ii f ti cu lt to provide inland waste disposal s;ites in mct ropol itan

zones .

1In 0,saka Sav:, the ma in bod*. of tlie bay for i ntervre !tec tuire waJstev~ o~

Osia j Inte :~r ert oe (oast~il Area L~nv ironmumen Imorovement Cen terý wa.s

to is Nirc'h !-,r aictual' work.

oI %iII )t O PR!l:.VEI TON ~H

:1L ~o~ ie ite:eoto -"'.en rin:R j'0111tilln v 0~~e oi I hroti.;h

t. tit Au. ~i,!ie'- o'r toei -waste oil r'cept ion1 11'i lit i 'S .

trc i '2.1 u aciit i,-' itt -'a ý)r b~ort.s wos c omp 1 vtod in11 1472 .

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13
I" !

PORT ENVIRONMENT IMPROVEMENT WORKS

Coastal waste disposal site

These sites are designed to receive all wastes including dredged materials, marine wastes resulting from cargo handling, urban wastes, and

industrial wastes.

It Pas become increasingly difficult to obtain 3ites in urban artas

for final disposal of wastes because of the progress in urbanization. Therefore, the demand fur water are-s for final disposal has increased in recent

years.

There are also strong demands for land to develop or renew port areas.

In response to such soLial needs, the government has been providing port

management bodies with subsidiL• for the construction of bulkheads of waste

disposal sites since 1973.

The list of wastes dumped in the disposal site is headed by surplus soil

produced by inlard construction works, followed by dredged material, general

wastes, and industrial wastes. Of the annual total of about 280 million tons

of general wastes and industrial wastes produced in 1979, about 140 million

tons went to final disposal, of which 6.9 million tons or 4.9% were disposed

of in coastal disposal sices.

Construction of cleaning vessels

Ports are generally closed waters, preventing frequent t-:hange of seawater. As a result, the refuse which flows in from rivers and Lhat produced

by port activities drifts in stagnant areas in ports, thus interfering with

navigation and marine activities. Mor-over, the drifts often cause environmental pollution through putrefaction, foul smells, and deposition, resulting

in water pollution and sludge. Accerdingly, prompt accumulation of this

refuse while still floating is desirable.

The government has been providing port management bodies with subsidies

for the construction of cleaning vessels necessary for the accumularton of

oil and floating refuse since 1974. Sixteen cleaning vessels have thus been

constructed in 15 ports as of 1981.

Parks and open spaces

We are also creating j pleasant port environment by providing greens,

open spaces, rest houses, etc., so that the ports can serve the local

residents.

Accordingly, the government provides subsidies for those port management

bodies which undertake the improvement of port environment by providing

14
greens, open spaces, etc., within their port areas. Those so far compleýtel

draw families on holidays and serve as a place of rel1xation w.ere tLe citizens

can get familiar with a port.

In 1980, greens were provided at 81 ports throughou: the country at a

total cost of V7.2 billion, accounting for 3.72. of the total ,irban park

improvement cost of ¥194 billion.

15
REMOVAL OF BoTrOM SEDIMENTS IN OSAKA PORT BY

I'HE PNEUMA PUMP DREDGE "SHUNKAI"

Shiro Kasaj ima

Manager of the Construction Division

Port and Harbour Bureau, City of Osaka

ABSTRACT

The Osaka Port, which is one of the representative ports in West Japan situated at the innermost

part of Osaka Bay, has been suffering from the sediment of mud polluted with organic substances on the

bottom of rivers such as Aji River, Shirinashi River,

and Kizu River due to wastewater from factories and

city sewage, which have caused deterioration of the

environment through pollution of water and generation

of a foul smell.

As a countermeasure, the Authority of Osaka City,

having ,noticed the excellent performance of the Pneuma

pump system, untertook the first mud dredging experiment in Japa, with that system (which was introduced

from an Italian firm S.I.R.S.I. in December 1971).

Through this experimental dredging, the suitability of

the Pneuma pump system to the dredging of polluted mud

was well proved.

As a part of the pollution control project of the

port and harbor, the Bureau completed the Pneuma pump

dredge "ShunKai" in July 1974, then organized a

dredging squadron with hopper barges that had undergone the necessary modifications. The squadron has

engaged in dredging operations of polluted mud since

November 1974 until the present day.

This paper introdt'ces the Pneuma pump dredge

"ShunKai" and the results of the squadron operation.

INTRODUCTION

The Port and Harbor Bureau has developed a new dredging process, the

Pneuma pump system, which is capable of dredging a high solids concentration at any depth according to the configuration of the sea bottom without

fear of secondary pollution. The Bureau ,as also built a new dredge to

promote Japan's pollution control project. This system was built because:

16
(1) unless care is taken when mud on the water bottom is dredged by a conventional grab dredge, the grab might penetrate the layer of muddy sediment and

dig into the comparatively hard soil of the sea bottom, and, when li fting the

grab, the adhering mud would cause contamination of adjacvnL waters; and

(2) if dredging is performed by conventional suction dredges and th- mud

transported to the dumping grounds on board box-shaped hopper bargeý , it

would not be economical due to a very low solid concentration.

OPERATIONAL PRINCIPLE OF THE PNEUMA PUMP

The Pneuma pump system consists of a pump body, a distributor, and a com- pressor. The pump body is composed of three cylindrical tanks that are used

as one assembly. Each tank is fitted with an inlet port, an outlet port, and

various valves. The distributor automatically controls charging of compressed

air to each tank with a constant cycle and then discharging it to the atmosphere. The compressor supplies the compressed air, the capacity of which may

vary according to the required performances, but its pressure is nor ally

7.5 atm. 7

When the pump body is lowered to the sea bottom with the distx' butor in

operation, the seawater comes into the tank lifting the inlet valve. Then,

compressed air is delivered via the distributor, and the seawater in the tank

is displaced (by the action of air similar to that of piston) throush the mud

discharge pipe. Then, the compressed air that filled the tank is diischarged

through the distrioutor into the atmosphere and the air pressure wit' in the

tank returns to atmospheric level. At this moment, the mud at the seabed is

forced into the tank due to the head difference between the surface and the

bottom and horizontal movement of the suction port. Thereafter, by repeating

the above-mentioned operations, the mud is discharged through the mud pipes. As this operation is repeated within a tank and the three tanks worki continuously with a constant interval, the mud is discharged continuously fiom the

mud pipe as shown Figure 1.

A

-- I-- ~

. ........

Figure 1. Principle of Pneuma pump

17
DREDGING TEST OF MUD WITH THE PNEUNA PUMP SYSTEM

One Pneuma pump 300/60 system and distributor were installed onboard tile

crane barge "No. 1 Konio" and one on the grab dredge "ShunKai." The dredging

tests were performed along the lower part of Kizu River, the innermost part of

Aji River Inner Port, Zone No. I Inside Port, and in front of wharfs A and I

of South Port with the following results being obtained:

(1) When dredging at a constant speed of from 1-3 m/min, the mud can be

dredged with a very high net solid concentration by volume as shown in Tables 1

and 2. The quantity of discharge also can exceed the rated capacity of the

Pneuma pump 300/60.

(2) The mud piled 11D on the guarding rubble mound in front of the wharf

can be removed without impairing the surface of the rubble mound.

(3) The trawling speed should be kept at the low level of 1-3 m/min and

constant.

(4) Anong the various types of shovels tested, the three shovel type,

the big shovel type, and the leg shovel type, the three shovel type was effective for both mud and soft clay. The shape of the shovels should be designed

to cope with the conditions of the site of dredging.

(5) Deposit of rubbish on the seabed or river bed caused little harm to

dredging.

(6) If the three shovel type is used, the blue-gray clay, the most common soil in Osaka Port, can also be dredged.

(7) Iron scraps and stones of small quantity can be dredged as they are.

(8) The degree of transparency of water near the surface at the dredging

site declines by about 15-20 cm.

(9) For mud having a very high solid concentration such as that dredged

by the Pneuma pump system, the application of pan-floc is not suitable.

CONSTRUCTION SPECIFICATIONS OF PNEUMA PUMP DREDGE "SHUNKAI"

(1) Basic Design Requirements

Soil to be dredged

Deposit of mud or soft clay in the duplication area of a river and

port and at the river mouths.

O Quantity of soil to be dredged S3

Dredgirnv, 3 transportation, and discharge of about 1,000 m per day or

210,000 m per year.

O Weather. sea, and geographical conditions

The sites of operation are within the calm water area in the Osaka

18
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are tidal and the velocity of flow is low, 0.5-1.0 kt along the

mainstream of Aji River and 0.5 kt along Shirinashi and Kizu Rivers.

For the weather and sea condition at the time of operation, the

design should comply with the terms of "Standard of Desiga for

Workiug Boats."

a) For the design of the hull, the maximum instantaneous wind velocity

shall be 16 m/sec during operation.

b) The velocity of tidal current of 3 kzs shall be cLasidered duting

operation.

c) The wave height during operation shall be 0.5 m (1/3 significant

waves).

d) The dredging depth shall be 15 m below the surface.

e) Process of disposal of dredged material shall be trawl dredging

carried out by the dredge fitted with the Pneuma pump 450/80. The

dredged mud is placed onboard 500-m 3 non-self-propelled hopper

barges. The barges are pushed to the disposal site in the. North

Port, making three trips or more per day, where the mud is

discharged.

(2) Design Considerations

Q Electro-hydraulic winches of stepless variable speed enable the -

vessel to travel at 1-5 m/min during dredging and 20 m/min maximum

speed on the return trip after dumping.

The centralized control station fo-. operation is provided as a

labor-saving device.

To prevent noise generated by the air compressors, each compressor

is confined in a separate soundproof enclosure with shock-absorbing

rubber inserted between the machines and the hull.

Providing for the dredging along the narrow channels in the upper

reach of rivers, fairleaders of christmas tree type are fitted at

the bow and the stern part of the vessel.

O The ladder system is used for lowering and lifting the Pneuma pump.

To maintain an agreeable working environment (including living area,

operating room, etc.), special silencers are used for exhaust noise.

A loader system with mud discharge pipes leading to the hopper

barges moored along both sides of the dredge is used for loading

the mud.

The specifications of the "ShunKai" and diagrams are shown in Table 3 and

Figure 2, respectively.

21

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ORGANIZATION OF S4QUADRON

"ShunKai" is required to dredge the narrow upper reaches of the rivers in

.the city. rhe hopper barges of the existing pusher barge line system cannot

be turned at the narrow part of ýhe waterway; therefore, two non-selfpropelled hopper barges of 30 m0 capacity were remodeled into the box-shaped

mud barges with 500 m3 capacity able to be pushed either from bow or stern.

"he squadron is organized with "ShunKai," a pusher tug, the two non-selfpropelled mud barves, and a chartered non-self-propelled bdx-shaped mud barge

of 50)0 m capacity.

In August 1977, a non-self-propelled mud unloading barge of sand pump

type (dispiacement 288.45 tons) was created by modifying the existing grab

dred.er "SeiKii" and installing the sand pump (mud discharging capacity

i 540 rn/hr) of DP 10)1 KL Type manufactured by Toyo Electric Co., Ltd. Thus,

ithe organization of the squadron of the total system from dredging, transporting, and unloading to final discharging is complete.

IMPROVFMENT OF DREDGING EFFICIENCY AND WORKING ENVIRONMENT

In 1976, when the dredging at the planned depth D.L.* -6.0 m was carried

out, the operational efficiency was too low and the solid concentration of the

dredged soil was much less than anticipated. Thus, improvement of the operation4l ef ficiencv of dredging at shallow depths has been required.

As a possible countermeasure, installation of a vacuum pump at the exit

of the distributor was examined, but the idea was abandoned because there was

little margin both in the capacity of the generator and the space for installation. however, taking advantage of the surplus of compressed air wheu the

dredging depth is shallow, the dredging efficiency can be raised by installing

the breathrider (vacuum generator).

Installation of the breathrider vacuum gained 0.20 m of water column and

allowed dredging at a depth about I m less than possible before. It further

contributed to Litt- improvement of dredging efficiency by remarkably reducing

the chances of choking of the shovels with mud. This can be attributed to the

fact that due to the effect of vacuum, the resistance against lifting the

suction valves by the pressure of mud and the same in the air pipes between

the pump bodies and the distributor during the cycle of delivery and suction

oi the compressed air is substantially reduced.

As a countermeasure for the offensive odor of hydrogen sulfide, an

absorption tower (which simultaneously works as a silencer and a solid remover)

wa's also installed. Within the tower the bad-sr~elling exhaust air is washed

by a seawiter shower, dehydrated and well diluted, and then released to the

atmoiphvre after bt ing led to the level of the topping mast. Thus, the

of,1 'asive odor is sccessfully reduced. The flow diagram of the system is

illustrated on the nrixt page.

* ). I. mean low wirer.

25
A I r-pE...oýr

RESULT OF OPERATION BY "SHUNKAI" SQUADRON

Procedure ofOpertion

(1) Prior to operation, the geological survey of the dredging area is

r.toducted and the thickness of mud to be dredged, ratio of water content, loss

en ignition, specific gravity, etc., are determined.

* 4 (2) The trawling dredge is used and the dredged mud is loaded onto the

mud barges of closed type. The volume of the muddy water is surveyed and

sampled.

(3) fhe mud barges are pushed to the disposal site by the tug. The mud

is discharged into the enclosed disposal site area surrounded by banks.

* (4) The quantity of the dredged soil is estimated from the ratio of

water content and the apparent specific gravity of the sample and the volume

of muddy water.

(5) For guidance, the dredg~-i sea bottom is surveyed by the echo sounder

and confirmed.

Manner of Operation

By August 1977, the operations were carried out in the following manner:

Dredging............... .by the Pneuma pump vessel "ShunKai"

Transportation.........by a pusher tug and three mud barges of box type

(one of which was chartered)

4 These operations were conducted by the Bureau. The prevention of secondary pollution is assigned to contractors. The disposal of surplus water is

assigned to Osaka Industrial Wastes Management Public Cooperation.

Upon completion of the mud unloading vessel "SeiKai" (September 1977),

the contracted operation of the barge unloader has been converted to direct

"operation by the Bureau. Other operations remain the ;ame.

qb

4

4 ae otn n h paetseiicgaiyo h apeadtevlm
Results of Operation

* Upon completion of "ShunKai," a series of tests was carried out to cope

with the various operational conditions.

•* Whether or not the centralized control system would work satisfactorily

was confirmed first and then the rate of mud discharge of each shovel, the

air pressure and air volume in the pump bodies, the quantity of air consumed, etc., were investigated.

Noise was also measured at every noise and vibration preventive structure

and was compared with -he design value. Whether or not the anchors would

have sufficient holdir; power to endure the load of trawling operation and

"* whether the winches ir -.talled for the trawling operation would operate at the

required speed for forward and astern travel were also investigated.

This operation began in November 1974 and by tne end of March 1982

dredging of polluted mud and disposal had been carried out at the locations

along Aji River, Shirinashi River, and Kizu River as shown in Figure 3.

Table 4 gives the operation results, and Figure 4 shows the results of the

echo sounding.

4 'he annual su mmaries are also listed in Table 5 with respect to the

dredged area and the quantity of dredged soil. The total dredged area and the

,quantity of dredged soil as of the end of March'1982 were 532,000 m2 and

3 1,460,600 mi3 , respectively, and the total quantity of soil removed was

2,551,700 m with an overall average solid concentration of about 57%.

The annual record of operation of "ShunKai" -is shown in Table 6. In the

operational hours of "ShunKai," time required for shifting both ways between

her moorings and. the site of dredging and the same necessary for taking the

bearings in order to fix the position of operation, about 400 hours per year

total, and another 100 hours for cleaning, during which the rubbish from the j muddy sediment is removed from the screen of the pump shovels, and time for

waiting, meals, and cleaning of the vessel at her moorings are included.

Solid Concentration of Dredged Soil

The solid concentration of the dredged soil is supposed to be influenced

by the grain size, thickness of the soil to be dredged, and the technique of

operation, but the correlation among these is not clear. However, in the case

of dredging by the Pneuma pump system, the deeper the water at the location of

dredging, the stronger the thrust due to hydrostatic pressure. Consequently,

a trend that the solid concentration increases proportionally to the water

depth can be observed, although there is some dispersion in the relation

between the water depth and the average solid concentration (see Figure 5).

27
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28
North wclw, of North Fort

South Ucflmm of North Ponl

T1woWr

Aiidrdw cy'h..L

-~ Ale dredped by t3he rbdrde g lwdbcett

Figure 3. Dredging operation sites

29
IN--

_ Before dredging I6--

After dredging is

w'1

__. to.'

Figure 4. Record of echo sounding

7 2 ) ....

L ))

2 10

6 7 8 9 1O N,

Water depth

Figure 5. Water depth and solid concentration

30
Table 5. Dredged Area and Quantity of Soil

Dredged for Every Fiscal Year

Quantity of

Fiscal year Area dredged soil dredged

1974 23,500 m 109,800 m

1975 90,300 222,900

1976 50,500 162,800

1977 43,500 170,000

1978 71,500 180,600

1979 75,000 190,000

1980 106,700 208,100

1981 71,000 216,400

Total 532,000 1,460,600

=4

Table 6. Summary of Operation of "ShunKai"

Fiscal, No. of days No. of days out No. of days Hours Hours of

year on operation of operation on service on service operation

1974 98 15 113 1,018.20 782.40

1975 207 55 262 2,117.15 1,552.10

1976 200 69 269 1,965.00 1,408.15

1977 214 30 244 2,109.00 1,589.00

1978 222 33 255 2,093.30 1,501.40

1979 220 37 257 2,044.15 1,453.25

1980 212 42 254 1,958.30 1,387.45

1981 245 20 265 2,430.15 1,569.50

31
COMPARATIVE INVESTIGATION OF TURBIDITY AT WATER SURFACE ADJACENT

TO DREDGING SITE

On March 9 and 27, 1979, turbidity of the water surface adjacent to the

dredging site was investigated. According to the results, the Pneuma pump

dredge makes the water at the lower layer turbid to a certain extent up to'

50 m away, because the pumps are dipped in the bottom mud; however, practically no turbidity is observed in the upper and middle water layers.

The grab dredge with the clou I bucket often operates with the bucket

not completely closed after a g-. due to the rubbish found scattered in the

mud. Therefore, the turbidity 50 m away from the dredge occurs throughout

all layers, surface to bottom, and tends to increase as the dredging continues.

As a typical example, the location of operation in Figure 6, the record

of transparency and turbidity 5 hrs after the beginning of dredging in

Table 7 and the comparison of the record of measured turbidity in Figure 7 are

presented.

MEASURES FOR PREVENTION OF SECONDARY POLLUTION

The dredging operation by the Pneuma pump dredge causes the release of

an offensive odor unique to the polluted mud, and an oily material mixed with

light organic dust emerges forming films on the surfaca of muddy water discharged into the hopper barges. The smell and oily material must be properly

disposed of and the dispersion of mud particles and suspended oily material

must be prevented as well.

Measures Against Foul Smell

The polluted mud sediment at sea bottom is in a state of anaerobic

fermentation and causes an offensive odor due to the gases generated such

hydrogen sulfide, methacabutane, and thio-glycolic acid.

To handle the foul.smell from the distributor, the release gas is thoroughly washed and diluted through the shower in the absorption tower and is

then discharged into the atmosphere from a high position. For prevention of

foul smell from the mud discharged, one bagful of deodorant agent (20 kg) is

spread over one bargeful of mud. The deodorant is composed of 95% bentonite,

4% phyroligneous acid, and 1% papain enzyme and eliminates foul smells through

the catalytic action and absorptive power of the ingredients.

Measures for Disposal of Oily Suspensions

When the polluted muddy sediment is pumped into the hopper barge, oily

substances mix with minute organic substances and float on the surface, forming foamy scums. In order to dispose of these oily substances, a half can

(18 litre) of neutralizer is first sprayed over a bargeful of mud. Then,

after discharging the mud, the same quantity of neutralizer is sprayed along

the boundary of the oil fences. These oil fences have curtains underneath

that are stretched around the discharge nozzle of the mud pipe. (The curtain

has a peripheral length of 300 m). The spraying is done by a pump and

32

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No.2N

0 '0O 7

14o.9 of Disrio

No.4 0

04 0 0

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Figure 6. Turbidity survey in the vicinity of Aji River Dolphin :

the neutralizer, diluted to about 20% solution, is ejected from the hose

nozzle.

Prevention of Dispersion

of Discharged Soil and

Countermeasures for Surplus Water

Prevention of dispersion and outflow of the mud, and quality control of

surplus water, both require a great amount of care. The disposal site, as is

its nature, has to accept an enormous quantity of muddy water in addition to

ordinary dredged soil, etc. Therefore, a facility for disposal of the surplus

water is attached to the disposal site.

At the North Port disposal site, the result of the bottom soil test and

the elution test is checked prior to disposal to ensure compliance with the

standard two drainage canals, four precipitant mixing stations, and a monitoring facility for turbidity automatically measure, record, and watch the

33

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Table 7. -Result of Survey on Transparency and

Turbidity of Aji River .

March 27, 1979 .

Weather: Fine, Temperature: 16 0 C During dredging operation at rising tide.

Turbidity_

Point of Time of Depth of Upper Middle Lower

measurement measurement water Transparency layer layer layer Remarks -

Pneuma pump dredge Sequence of

No. 1 13:53 11.0 0.5 13.0 11.0 8.0 measurement 3

2 10.5 0.6 13.0 11.0 4.0 2

3 13:53 10.0 0.6 13.0 10.0 4.0 1

4 11.3 0.5 12.0 10.0 6.0 4

5 10.0 0.6 12.0 11.0 5.0 5 4

6 10.7 0.5 14.0 10.0 10.0 8

7 10.7 0.5 14.0 9.0 9.0 7

8 11.5 0.6 14.0 9.0 7.0 6

9 9.0 0.5 12.0 10.0 6.0 9

10 14:03 9.0 0.6 13.0 11.0 6.0 104

Grab dredg2 of closed bucket type

No. 11 5.0 0.4 20.0 38.0 40.0 3

12 5.4 0.6 13.0 12.0 9.0 2

13 .4:06 5.0 0.6 13.0 12.0 12.0 1

14 5.0 0.5 16.0 35.0 80.0 8

15 14:16 9.0 0.6 15.0 14.0 7.0 9

16 5.8 0.5 15.0 14.0 30.0 5

17 6.0 0.6 14.0 18.0 25.0 6 .

18 6.2 0.6 14.0 13.0 25.0 7 "

19 4.0 0.4 23.0 / 13.0 4

Upper layer: 0.5 m below surface Middle layer: 2 m below surface

Lower layer: 2 m above water bottom

I3

35 -i

I

/
quantity of suspended substance and values of COD and pH so that the quality

V-• of surplus water can be controlled.

The device for discharging through slits at the end nozzle of the pipe

line and the oil fence effectively prevent the primary dispersion of soil

particles and promote their precipitation.

Transparency tests of the water samples taken from the surface, middle,

and bottom layers outside the oil fence show that turbidity disappears 400-

500 m outside the oil fence.

FUT1RE PROGRAM OF DISPOSAL OF POLLUTED MUD SEDIMENT

L At present, the operations for 1982 of the Five Year Plan of Prevention

of Pollution Project of Osaka Port (1981 - 1985 fiscal year) are under way.

The following quantity of disposal is planned for each river in and after

"1982:

3

Aji River 278,900 sm

Shirinashi River 141,300 m3

Kizu River 157,900 m 3

3 Total 578,100 m

For guidance, the total dredged soil accepted by the site of disposal in

North Port was 11,887,000 m3 by fiscal year 1981. Although the polluted mud

sediment of 1,461,000 m3 dredged, transported, and discharged by the "ShunKai"

squadron is included in the above, this quantity accounts for only 12% of the

total dredged soil.

, In 1984, accept:i' i the dredged soil in the Northern Area will be

termin ted. In and if-ur 1984, acceptance and disposal of general dredged

soil and the polltA' mud will be made at the Southern Area (capacity of

acceptance 46,00iO00 m3 ).

The Pure.ri intends to convert both disposal sites, the Northern and

Southern area of North Port, into newly reclaimed land through intensive

application of various soft ground methods of improvement. Then these new

lands can contribute to the future development of Osaka Port.

.9POSTSCRIPT

The author is confident that the very emergence of "ShunKai" has opened

a new way to the dredging of polluted mud. He also earnestly hopes to attain

more complete mud dredging techniques through further application of new

technologies in the futurt.

36

0
BIBLIOGRAPHY

"1. "Sagyosen" No. 82

i Report on dredging experiment with Pneuma pump.

2. "Sagyosen" No. 93

Outline of the design of the dredge "ShunKai.'

3. "Sagyosen" No. 103

Report on the dredging operation of the Pneuma pump dredge "ShunKai."

3

37
1. The "ShunKaill4 Carri age by a pusher boat and

a box barge'

I?

1) fr v d gii i v 5. Oil treatment by

neutralizing agent

4w

I' ad Irl h'~" . iaI p ti

100d
• 7. View of the dispos•al site 10. Transparency test

' of water sample

p.

,.• .S tO. nirc:led oil fence 11. New and old plate valve

wiLh curt~iin for inlet in a pump body,

, ..

Jar

8r. *-n.it off 1ol.(ing oii 112. A and oma ld p;iI a fv r

01 th",LicTS• site. mtid (it-, liverv

39

iihutmnfo nlt In a pupbd
F

CONSTRUCTIVE USE OF DREDGED SAND

N.E. Parker, P.E.

Coastal Engineering Research Center

Kingman Building

Fort Belvoir, Virginia 22060

ABSTRACT

Two obvious opportunities for constructive use of large

volumes of dredged sand are beach preservation and offshore

bar construction. To date, research has focused on beach

preservation. Technology to place dredged sand directly on

the beach has been developed and is now routinely used.

Technology to place material offshore for distribution on the

beach by natural forces has not yet matured. Considerable re- V search designed to define the limiting depths within which ÷, natural distribution will occur has been undertaken both in

the laboratory and in the field. Some of the most compre4 hensive work was done by the Corps of Engineers Coastal Engineering Research Center in 1976 and 1978 using a split-hull

barge and a split-hull hopper dredge for sand transport and

placement. In the 1976 experiment, 27,000 m3 of sand was

"placed in a single mound between -2 and -3 foot contours. In

the 1978 experiment, almost 34,000 m3 was placed at three

different depths averaging 2.7, 3.6, and 4.7 meters. These

experiments generally confirmed the feasibility of beach nourishment by placement of dredged sand in relatively shallow

water. To date, little research aimed at the development

of technology to construct offshore bars in depths adequate

for the operation of medium and large hopper dredges has been

undertaken. Little information is available about the stability

of such bars, their effect on the shoreline, or their effect on

wave climatology.

4 INTRODUCTION

Background

The construction and maintenance of coastal harbors and navigation channels

"has always involved dredging of large volumes of material - much of it sand.

4 Over time, the amount of material dredged has steadily increased as the depth

demands of shipping have increased. In the United States, sand has long been

in abundant supply and readily available from conventional upland sources at

a modest cost. Consequently, sand as a natural resource has been taken for

granted. For a variety of reasons, sand from conventional sources has become

increasingly more expensive and less readily available in recent years. As a

40

I4
*- consequence of the decreasing availability from conventional sources and the

increasing volume of dredged sand, recognition of the importance of dredged

sand as a natural resource has been growing during the past 2 or 3 decades.

At the same time, concern about the ultimate consequences of wasting this resource at sea has mounted. Considerable attention has been given - and continues to be given - to constructive use of dredged sand. In the marine environment, the two obvious opportunities for the constructive use of large

volumes of dredged sand are beach preservation and construction of offshore

bars. Most research and development has focused on technology for beach

preservation. Little effort has been made to develop technology for bar con- 5 struction.

2'" Beach Preservation

Eroded beaches are usually restored by an initial' placement of sand to

return the beach to a selected pre-existing dimension. The restored beach

often continues to erode, necessitating periodic placement of additional

sand to nourish the restored beach. The Corps of Engineers is actively

engaged in a program of beach restoration and beach nourishment in the United

"States. Beach restoration is usually accomplished by direct placement: of

sand on the beach proper. Beach nourishment is usually accomplished by simi-

"lar placement or by placement of sand to form a feeder beach from which natural

forces will distribute sand along the beach to be nourished. For both activities, sand is often mined from offshore deposits by dredges. Beach preservation can be - and sometimes is - combined with harbor or chRnnel dredging to

permit constructive use of the dredged sand. Technology to place sand so

dredged or mined directly on beaches or feeder beaches is quite well developed. Both hopper and pipeline dredges are routinely used. Direct placement is effective and is a constructive use of the dredged sand resource but

economic and other advantages may be realized from offshore placement of

nourishment sand. Waves and wave-induced currents active in nearshore waters

are a natural transport system that will distribute sand along a shore. Much

"investigative attention has been devoted to definition and understanding of

this littoral process but definition and understanding are still quantitatively

imprecise. Effective utilization of the littoral process in beach nourishment

actions involving offshore feeder sources requires definition of the seaward

limit of the zone within which natural transport success is predictable.

"Efforts to that end have been made and are continuing. Summarization of the

results of those efforts is the primary purpose of this paper.

Offshore Bar Construction

Recent dialogue about constructive use of the dredged sand resource has included offshore bar construction. Although large volumes of sand can be used

to nourish and restore beaches, a number of economic and other considerations

combine to more or less limit this use to instances where pipeline or small,

shallow-draft hopper dredges are used. Medium and large hopper dredges cannot

operate within the effective littoral transport zone unless a' pump-out terminal

with proper approach channel is established. This option is quite often not

available and is always relatively costly. Additionally, there are practical

41
-J

limits to the volumes of dredged sand that can be used to nourish beaches

.. near harbors and channels. There seem to be no practical limits to the

-" volumes of sand that can be used to construct offshore bars in water

"depths in which medium and large hopper dredges can operate. Such bars

would most certainly interact with the physical environment in which they

were sited. Precise interactive effects are not readily predictable

from present knowledge and understandings but present knowledge and understandings do permit general predictions with considerable confidence.

Interactive effects will be subtly rather than boldly expressed and subtlety

Swill increase with increasing depth of water over the bar. Some shoreward

movement of sand from the bar may occur but the volumetric rate of movement

will be quite low and will be an inverse function of increasing depth. At

* the depths suited to large hopper dredge operation, losses of sand from the

.,bar are apt to be quite slow or negligible and consequently any changes in

* configuration will be very gradual. The presence of the bar may alter the

wave climate somewhat. In depths suited to operation of large hopper dredges,

1 the amplitude of all but extreme event waves is not likely to be affected

but the period of long period waves may be reduced. This and the physical

barrier effect of the-' bar may combine to restrict seaward movement of material

eroded from the beach area. Little investigative attention has been given to

"these and other interactions.

OPertinent Beach Nourishment Research

Several experiments have been conducted to examine the efficiency of beach

nourishment from offshore feeder sources. Two beach nourishment projects have

been completed, in which the nourishment sand was placed offshore.

A two-dimensional laboratory study which simulated small and large storm

conditions of the Great Lakes wave climate was reported by Kamphuis and Bridgeman in 1975. This showed that, under the controlled laboratory conditions,

sand properly located on the profile and placed at the proper time in the

season would move shoreward and accrete to the beach.

Three field experiments were conducted prior to the 1976 and 1978 experiments described later in this paper. Sand placed offshore in the experiments

at Long Branch, NJ (Hall and Herron, 1950; Harris, 1954), Atlantic City, NJ

(Hall and Watts, 1975), and Santa Barbara, CA (Wiegel, 1964), were not fully

successful or conclusive. At Long Branch, 460,000 m3 of sand placed in 10- to

12-meter water depths either did not move or moved "haphazardly." At Santa

Barbara, 153,000 ml of sand placed in a 1.5-meter-high mound in 6.7 meters of

water showed no significant change in configuration 9 years later. At Atlantic

City, sand was placed in 4.5 to 6.1 meters of water but postplacement observations did not develop enough information to evaluate its behavior.

Beaches at Copacabana, Brazil (Vera Cruz, 1972), and Limjford Barriers, Denmark (Mikkelsen, 1977), were successfully mourished from feeder sources placed

in water depth of 4 to 6 meters.

42
In 1976 and 1978, field experiments were conducted by tie Corps of Engineers

Coastal Engineering Research Center at New River, NW. These are the most comprehensive investigations undertaken to date. The remaindeT of this paper summarizes those experiments. Detailed reports are in Technical Paper 80-1,

Coastal Engineering Research Center, by Robert K. Schwartz nd Frank R.

Musialowski, and a Technical Paper to be published, Coastal Engineering Research Center, same authors.

1976 EXPERIMENT

Purpose

"The experiment was designed to test and evaluate the hypothesis that sand

"dredged from a coastal inlet and placed seaward of the surf zone will effectively

Snourish the downdrift beach. The means for doing this became available when

the self-propelled split-hull barge, "Currituck," was placed in service in 1975.

The "Currituck" is shallow draft and can dump in 2 meters of watcr. Fully loaded,

its capacity is between 200 and 300 m3 . It was loaded by alside-cast dredge.

The location for the experiment was New River, NC, which islabout 60 km northeast of Wilmington, NC. The beach southwest of the New River Inet (West

Onslow Beach) was the nourishment target. The beach is about 60 m wide,

backed by a vegetated foredune, and only slightly developedi

Definitions '

The offshore zone extends from the surf zone to the seavard edge of the

Continental Shelf. The nearshore zone extends seaward fromithe shoreline well

beyond the surf zone and defines the area of nearshore currents. Nearshore currents comprise the current system caused primarily by wave action in and near

the surf zone. The surf zone extends from the limit of wav4 uprush to the

outermost breaker. Near shore and offshore zones overlap and lack a distinct

boundary. The seaward limit of this experiment is within t e overlap. In this

paper, offshore refers to any point seaward of the surf zone.

Procedures

Placement of sand in the test area began 19 July 1976 and continued for

26 days. The "Currituck" placed a total of 26,750 m3 along 'a 210-meter reach

between the 1.8- and 4.0-m contours. The tidal range was about I m. Monitoring

began 7 days before the start of placement and continued 71 days after completion of placement (12 July to 19 October).

'rofiles extending across the beach and nearshore zone were measured at

30-m intervals in a 270- x 300-m area. The shore normal dimension (300 m) extendd from the base of the foredune some 240 to 270 m beyond MLW to an approximate water depth of 4.5 m below MLW. The beach leg of each profile was measured

using standard rod and tape surveying techniques. The seaward leg was measured

using a towed, bottom-riding sea sled with mounted stad'a board (Musialowski

43
and Schwartz, 1979). The sled was towed seaward to the outer station on the

profile line and then pulled landward by a shore-based winch. Position and

elevation data were obtained as it was pulled shoreward. The profile data

were used to calculate volumes between adjacent profiles.

Sediment samples were collected from the upper 2 cm of the seabed at 7.6-m

intervals along a profile line near the middle of the study area. Current

velocity and direction, breaker height and period, angle of wave approach, and

wind velocity and direction were measured from 14 July to 16 September using

Littoral Environment Observation (LEO) techniques (Bruno and Hippaka, 1973).

Aerial photographs were used to document beach and offshore feeder pile configuration and to examine nearshore circulation in the placement area. Several

curren* meter measurements were made to document current distribution.

Physical Environment

Before the experiment, the beach was fronted by a shore-parallel, semicontinuous bar located in the outermost part of the surf zone. The beach

and nearshore sands were fine grained (0.14 mm) and well sorted. The tidal

range predicted for the study period had a mean of 1.0 m and a spring of 1.1 m.'

Breaker heights ranged from about 0.1 m to about 1.6 m and averaged 0.55 m

i with a standard deviation of 0.26 m. Breaker periods ranged from about 1

second to about 1z seconds and averaged 7.3 seconds with a standard deviation

of 1.8 seconds. During the placement period, summer oceanographic conditions

prevailed. Breaker heights were usually less than 0.6 m and breaker periods

were usually shorter than 6 seconds. Waves generally came from the southerly

direction. During the latter part of the experiment, winter oceanographic

conditions dominated. Breaker heights were commonly greater than 0.6 m and

breaker periods were typically longer than 7 seconds. Winter currents were

typically southwest at 23 m per minute whereas summer currents were northeast

at 18 m per minute. Currents were wave induced throughout the experiment;

the Lest area was outside the influence of inlet-associated tidal currents.

Results

The mechanics and volumetric rate of placement more or less dictated the

creation of separated but very closely spaced rectangular piles of sand

arrayed shore parallel with long axes normal to the shore. The individual

piles were about 9 x 25 x 1.5 m. Collectively, these piles formed a local

shoal which caused waves to deform and break. The more seaward parts of the

shoal were subjected to less wave breaking than were the more landward parts

because the water therc was deeper over the shoal. In the short term, the

wave and current rewording of the shoal coalesced the individual piles into a

generally shore parallel bar seaward of the naturally occurring surf zone bar.

The bar thus formed migrated shoreward but never reached the surf zone bar.

The migration rate was sporadic and reflected the degree of wave activity. As

the bar neared the surf zone bar, it was either eliminated or became rounded and

much reduced in relief. During the last month of the experiment when storm

conditions prevailed, the profiles in the placement area accreted in the offshore

zone. Accretion was also evident on profiles outside the placement area indicating

44
\ //7

that this accretion was a redistribution of sediments independent of the experiment. The surf zone bar landward of the placement area eroded or was displaced

landward. At the same time, the surf zone trough filled and became an extension of the foreshore. Adjacent to the placement area, the surf zone trough

.also filled but the surf zone bar remained stationary.

During the first month after placement was completed, a large decrease in

volume in the offshore zone was noted. About 75 percent of the placed sand

was apparently removed during this. period. Adjacent to the updrift side of

the placement area, a slight increase in volume was measured. Adjacent to

the downdrift side of the placement area a substantially larger volume gain

was measured. Volume changes in the inshore zone were similar but of lesser

magnitude.

1978 EXPERIMENT

Purpose

In the 1976 experiment, placement was essentially in a single mound at a

single depth. It showed that the sand so placed was distributed by littoral

processes. The 1978 experiment was designed to test and evaluate the effects

of increased pla'cement depth on postplacement transport. To do this, placement in several mounds and at different depths was planned. The 1978 experiment differed from the 1976 experiment in 3 important aspects other than

placement patterns. The 1978 experiment was designed to continue for at

least 12 months. The "Currituck" was modified by the addition of drag heads

and pumps and became a small hopper dredge instead of a self-propelled barge.

The Coastal Research Amphibious Buggy (CRAB) replaced the less versatile sea

sled as a surveying vehicle. The 1978 experiment, like the 1976 experiment,

was conducted at New River, NC. West Onslow Beach remained the nourishment

target.

Definitions

The terms used in discussing the 1978 experiment have the same meanings as

for the 1976 experiment.

Procedures

Sand was placed in three different water depth locations during July and

August. The average water depths at these locations were 2.7 m, 3.6 m, and

4.7 m. A total of 33,900 m3 was placed in 35 days. Monitoring began in June.

Data collection devices were mounted on the CRAB which carried a horizontal

positioning system interfaced with a shore-based minicomputer. Elevations were

measured by a shore-based level and the CRAB stadia board.. Both position and

elevation data were recorded on tape. This semi-automated data collection

45
system provided significant in-field data reduction, allowed real time tracking

of the vehicle, and permitted real time analysis of profile shape. The quality

of data benefited accordingly.

Profiles were measured in the same pattern as in the earlier experiment in a

490-m x 450-m area.

Vibracores were taken along selected shore normal transets using a CRABmounted portable vibracoring system (Lanesky, Logan, Brown, and Hine, 1979).

Divers collected sediment samples from the upper 20 cm of the seabed along

3 profile lines.

Physical Environment

Tne physical environment was essentially the same as for the 1976 experiment.

Results

As in the 1976 experiment, sand was placed in rectangular piles about

9 m x 25 m x 1.5 m. At shallow water locations, the piles were grouped as

in 1976 and in short term coalesced to form pseudo bars. At deeper water

locations, piles were placed on top of one another as well as side by side.

This placement produced 2.5-m-high mounds with water cover of about 0.6 m.

Wave and current reworking of all three bars occurred as in 1976 and with

similar results. The early volumetric loss rate measured from inshore

was very comparable to that measured in 1976. The loss rate decreased with

time but movement out of the placement area was still evident a year after

placement. The bar formed by placement in the intermediate depth area also

migrated landward and underwent relief reduction. Both were at somewhat lower

rates than the shallow depth bar and both decreased with time. The bar remained a distinct identifiable feature for a longer time period than did the

inshore bar. The bar created by placement in the greatest water depth area

migrated landward at a slower rate than either of t'-e two inshore of it and

the volumetric loss rate from it was markedly less than for the other two.

No lateral movement of this bar was discernible during the first five months

after placement.

In the test area as a whole, the bars formed by sand placement migrated

landward and laterally albeit at different rates. This migration was most

evident during the first 6 months of the experiment. At the same time, the

volume of sand contained in the bars diminished. No seaward displacement

occurred. These observations were confirmed by textural changes in bottom sediments in the area. The rate at which the bars were modified was greatest for

the most landward bar and lowest for the most seaward bar. The highest initial

volume changes were at locations in or near the breaker zone.

46
CONCLUS IONS

Shallow draft, split-hull hopper dredges can place dredged sand just seaward of the surf zone so that it will move onto and along the beach. Such

dredges can also maintain shallow-draft navigation channels including entrance

channels through tidal inlets. Shallow-draft, split-hull hopper dredges are

therefore quite competent for sand bypassing at tidal inlets and for the constructive use of dredged sand in beach preservation activities. No further

laboratory or field experiments seem warranted but large-scale demonstration

projects should be planned. Such demonstration projects should be monitored

until the technology is judged mature.

Demonstration of the effectiveness of shallow water placement of dredged

sand for constructive purposes is a partial answer to concern about wasting

an important natural resource. The larger question about constructive use of

sand dredged by medium and large hopper dredges remains. Offshore bar construction should now be addressed by a large-scale demonstration. That demonstration should be designed to determine whether the sand remains where placed,

"whether the bar modifies the wave and current climate, and whether the bar

modifies shore normal sediment transport patterns.

J. I, 47

bo-
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BRUNO, R.O. and L.W. HIPPAKA, Littoral Environment Observation Program in the

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4-.

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')0
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NJ. 1964.
RECLAMATION WITH SOFT SEA BOTTOM SEDIMENTS

Yasuo Shiratori

Hideo Kato

Sludge Treatment Laboratory

Machinery Division, Port and Harbour Research Institute

Ministry of Transport

ABSTRACT

When dredging soft sea bottom sediments, it is

important to •stimate the suspended solids (SS) concentration in the effluent from the overflow weir. In

some cases, special effluent treatment methods must be

adopted to meet the SS concentration level and environmental quality standard. One effective means for reducing the SS concentration level of the effluent is ro

employ the SS removal ability of the diked containment

area through the hydraulically appropriate layout of

inlet/outlet or baffle walls in the containment area.

To estimate the effluent SS concentration and to evaluate the sedimentation promotion, model tests were performed

on the influence of the SS concentration in the influent

and on the effect of inlet/outlet layouts and installation

of baffle walls in the containment area.

In model tests on the influence of the SS influent

concentration on that of the effluent, fly ash and Kibushi

clay were used as testing materials in 20 cases where the

influent SS concentration was varied 0.2 - 100 g/i and the

number of steps of overflow rate was 2. The SS runoff

rate tends to decrease with the increase of influent SS

concentration, and an experimental equation of SS runoff

rate was obtained. Effluent SS concentration had the

peak value at around 10 g/, of influent SS concentration.

In the model tests on the sedimentation promotion

effect of the inlet/outlet layouts, fly ash was used as

testing material in 30 cases where the concentration

* was 10 g/; and the number of types of layout and structure was 11. The four ste s of overflow rate covered

00.139 -I to 1.39 x 101 m/sec. The layout types

were divided into two groups according to their

characteristics. One group showed the value of SS concentration smaller than c., calculated from the formula

of ideal settling basin; the other group showed a value

larger than Cq. Good sedimentation promotion effect

"was obtained even in the simple types.

In the model tests on the sedimentation promotion effect of baffle walls installation in the con-

.9 talnment area, fly ash was used as testing material,

52

r
at a concentration of 10 g/k, in 30 cases. The number

of types of baffle walls installation was 10, and

overflow rate was as before. In the small overflow

rate raage, SS concentration of effluent in any

baffle wall installation type was approximately

equal to that of the ideal settling basin. However,

in the large overflow rate range, a high sedimentation promotion effect was observed in the submerged

cross dike.

INTRODUCTION

When pump dredged sediments are disposed into the diked containment area,

water pollution will not occur around the containment area by the effluent if

dredged sediments are good quality sand. However, attention must be paid when

the dredged material is small in particle size like silt and clay and polluted

by organics or toxic matters. When an adverse impact on fishery may be

expected, theselection of dredging period, restriction on the operation of

pump dredge, or effluent treatment must be considered. In all cases it is

important to know the relationships between effluent quality and dredged

material, reclamation area, and operating condition. In this report, the

authors tried to investigate SS that did not settle in the containment area

and ran-off with the effluent. The SS concentration correlates not only with

turbidity, but also with quantity of toxic matters in the reclamation of

bottom sediments containing toxic matters. Therefore, SS concentration is a

basic and useful measure of water quality.

In the field of water works and sewage treatment, SS removal in the

settling basin has been studied and many references are available

(I - 3, 8, 9).. These basins, however, are fairly different from the diked

containment areas for reclamation with dredged material, so only the basic

ideas of the literature can be useful, but this is not sufficient. For this

reason, as for soil particle settling in the containment area, more studies

from a different viewpoint than water works and sewage settling basin are

needed (4 - 6).

rhe main features of containment areas are as follows:

a. Various shape, area, depth of containment areas.

b. High SS concentration of influent.

c. Inlet (intluent loading pipe) and outlet (effluent weir) are

generally small and can be considered as points.

d. Water depth of the pond is small relative to the water area.

e. Quality and quantity of influent are not uniform.

f. Water depth and water area decrease with the process sf reclamation.

g. In many cases influent loading rate (overflow rate) is small compared

with other water treatment, but influent ruantity is large.

53
Some of these features appear strong or weak in each reclamation work, so the

phenomena are generally complicated and difficult to explain. In other words,

*' there may be cases in which the phenomena appear in one work, but not in

another, or the same SS treatment method is effective in one work, but not

effective or detrimental to another work.

The authors of this paper are studying the estimation of the effluent SS

concentration and the promotion of the removal effect of soil particles in the

containment area. This report introduces model tests conducted to explain the

relationships between influent SS concentration and that of effluent, SS

reriloval effect promot.on by inlet/outlet layout types and structures (11, 12),.

and SS removal effect promotion by the installation of baffle walls in the

containment aiea (7, 10). These relationships are compared with the effluent

SS concentration. This study is now under way, and the analysis may not be

sufficient and che model test method may need further consideration, but

qualitative results were obtained and are presented herein.

MODEL TESTS

Similarity of Model

Model test results are significant and easy to transform if the similarity

law between real and model is clear. In model tests that treated fluids like

water, tests where there was no free water surface (a pipeline) were conducted

"* based mainly on Reynolds law, and tests where there were effects of free water'

' surface (ports and harbors) were based on Froude's law. But, in model tests

of containment areas neither of these similarity laws is suitable. Water

surface gradient by gravity cannot be simulated using the similarity law of

Reynolds, and flow pattern like swirl caused by viscosity cannot be simulated

when using the similarity law of Froude. In addition to these hydromechanical

problems, the modeling of settling particles is one of the difficulties

encountered in model tests of settling basins. In some model tests on ports

and harbors, settling particles of modified specific gravity can be used to

suit the similarity law of Frou'd. On the other hand, there is the method

where the real settling particles are used for simplification of testing. In

the latter case, settling phenomena will be distorted based on Reynolds' or

Froude's laws if the model settling basin is geometrically similar to the real

one. For this reason, the concept of an ideal settling basin perpendicular in

two dimensions is introduced, where the model settling phenomenon is similar

to the real one. This is called "similarity of overflow rate" and is used

S widely in the water treatment field. In this, the hydromechanical aspect

decreases because the settling phenomenon is treated as ideal, but the

velocity term in the model is equal to that in the real. It is smaller than

that by Reynolds' law and larger than that by Froude's law, so the value of

K the velocity term by the law of overflow rate lies between the two laws.

Models in this paper are not the model of a particular real containment area.

Comparisons among many test cases are shown, where model specification was

determined mainly by similarity of overflow rate.

'-Xy1 erimental _t 4 mmn t

The model containment area is 6.8 x 2.5 x 1.0 m (Figure 1). Water depth

was usually 0. i m in the model tests. '[h, velocity of influent at the inlet

*)&
-

" y 1=68mM

"2.5 ,-0

E

IN -1.25 OUT

'" 0Q75 0

Q25 4 i0 -La'7' 6.29 1.0 x

0 Q510 20 4.0 6.8 X (m)

"Z h:0.1 m S

| •-•-o~~.34 m *' TFigure 1. Model containment area

*pipe of the real vin' (noted ' in case of real) was assumed to be 3 m/sec.

The basic shape of inlet pipe was a ro,':.J tube, and the outlet was a rectangular weir. The inlet velocity of th,: model vin was determined by the similarity law of Froude; D was determined according to the overflow rate of each

test case; and the static head of the overflow weir H was also determined

according to the overflow rate. The model basin is shown in Figure 1, and

the plan layout of experimental apparatus is shown in Figure 2. When the

model scale ratio is assumed to be 1/100, the main dimensions of the real

, containment area are shown in Table 1.

LEGEND

1 MIXING TANK 6. INFLUENT LOADING PIPE

2. STORE TANK 7 EFFLUENT WEIR

3 CIRCULATION PUMP 8. CONTAINMENT AREA

4 SLURRY PUMP 9. AUTOMATIC WATER

5 PIPE LINE SAMPLER

Figure 2. Experimental apparatus

-'-
Slurry was made in the mixing tank (0.6 m ) by adding testing material

and fresh water, and pumped to the store tank. Slurry in the store tank

(0.6 m3 ) with a stirrer was discharged into the containment area at a specified loading rate and velocity. The containment area was initially conditioned

by filling with fresh water up to the top level of the effluent weir and allowing to stand.

Testing Material

In model tests on particle settling, materials with a different specific

gravity from that of the real ones may be used. But modeling of the particles

is difficult, especially in cases where the particle size or the settling

velocity has a range of distribution; in these cases, real particles were

used in the model tests. These experiments used no particular type of real

soil particle; in cases where the settling velocity of the particles is dis-

"tributed, fly ash and Kibushi clay, which are easy to handle in model tests,

were used as testing materials.

The specific gravity of a fly ash particle is 2.1 and in it different

colored particles can be observed. Kibushi clay particles are 2.6 in specific

gravity and homogeneous in color. Figure 3 shows the cumulative particle-size

distribution of both testing materials by Coulter Counter method. Volume per

unit weight of each material in water differs by the quantity of the sample.

Figire 4 shows the results of the column tests in which 100' g of testing

materials was added to water to make a 1-k mixture. After 24 hours of line

settling, the volu~me per unit weight of testing material was 1.23 mk/g for

fly ash and 2.43 mZ/g for Kibushi clay.

I

100

5 0

0

0.1 1 10 100

Op ('Um)

Figure 3. Cumulative particle size distribution

56
'010

x - .

0 .4 C14

C~C;

co 14-4 -4x.4 r

1-4 0 0

00

rd 0-. ' c

00 ~ fo CC"C C,; C;

0E 0 I c"i

,40

-40

4 -4

.0 0 w 41 >0 IV w -44m 1

.0 71a0 0 0 0 C6 -4 u4- 1.0 l4'4

41 OU) C) wU: 4.4 41J C W- 0J 0. ( co 0. cu a) 0.rU) "AI 0 --j-4 4J w V) 4

'0~~- 0 ). 0 0 n0 0 0) In -4 U) C.1-

-4- U1O 

:3 U)O -$.~ 0-4 0 J.~.4 57 .' 
i

10010

Figue 4.Rslts f th coumn tests

i• i 400-

200-

S0 2 10 100 ,1000 1000

t (nrin)

Figure 4. Results of the column tests

Particle settling velocity is affected by the concentration of the par-

- ticles and decreases with the increase, of the concentration of the particles (13). Settling tests were conducted to investigate the settling characteristics of the testing materials using a settling column 30 cm in diameter - and 100 cm in height. After stirring the mixture, the water was sampled at

"* certain time intervals at a fixed point. Figure 5 shows a plan of the ,settling

(. 300mm

E

E

E

C

0

Figure 5. Settling column

,. 58
"column. Initial sampling depth is 30 cm, and sampling quantity is 0.5 - 1 9

at a time, so the sampling depth S gradually decreases.

Figures 6 and 7 show the solids concentration in the sample water in

relation to the initial concentration of slurry. For fly ash with an initial

"concentration C0 of 0.1 and 1 g/Z, the cuncentration of the sample C decreases

"gradually with the lapse of tiime. Plus, C is higher for 1 g/£ C0 than for

0.1 g/k Co. However 10 g/. CO represents line settling and C becomes lower

"than that for 1 g/Z CO after a certain amount of time. This tendency is

observed more clearly for 100 g/Z CO, and C becomes lower in the clear water

above the boundary line than that for 1 and 10 g/Z Co and is about the same

value as 0.1 g/Z Co. A similar tendency was observed for Kibushi clay, but

the line settling velocity was smaller compared with fly ash.

Figures 8 and 9 summarize these results in the form of cumulative settling

velocity distribution. In case of fly ash, it represents line settling at the

initial concentration more than 10 g/Z, and when initial concentration is less

than 1 g/i, where the settling mechanism is discrete settling, it makes no

difference in settling velocity distribution.

Fly ash

1 0.1 9/I

10LA• 01

_0 •• A 110

13100

C, L

t~t

1 0

I I oo

10 1 1 * emI,1

Sa 0

1 "a' , • 0 -

0 1 10 10 0 0' 10S

t (min)

Figure 6. Solids concentration in the sample

wat,_r, fly ash

59

I
K. clay

* 0.1 gA

01

a 10

p. 0 100

A/

E °

a;o

10 - • A

0 1 10 10 10'

t (minm)

Figure 7. Solids concentration in the sample

water, Kibushi clay

1.0

0 Fly ash Co 0.1 q/1 I

0 1

0

A t10

:> 0.5 0 100 o 0

tL. 0 * oO

0 -7 0 S10-

10 106 10 10 10-

VS (m/s)

Figure 8. Cumulative settling velocity

distribution, fly ash

60

*.7
1.0

.K. daoy 0 Co= 0. 1 g/! a

S10 0

0.5- 100 0 A 

-0 IfA

00

8

0 00 • •• ^ •, 3.• 

10"110 10-1 16-4 0-

VS (m/s)

Figure 9. Cumulative settling velocity distribution,

Kibushi clay

Kibushi clay (Figure 9) shows almost the same characteristics at a CO of

0. 1 and 1 g/L, but the settling velocity seems to become larger at 10 g/I

* Co. For 100 g/t Co, however, the cumulative distribution curve varies sharply

at line settling velocity so the weight percentage of the particles whose

velocity is larger than line settling velocity becomes smaller and also the

weight percerutage of the particles whose velocity is smaller than line

settling velocity also becomes smaller.

Based on the cumulative settling velocity distribution shown in Figures 8

and 9, SS runoff rate in an ideal quiescent settling basin was calculated

using the formula of Hazen and Camp (1), and that in completely mixing

settling basin was calculated using the formula of Hazen and Molina (3).

These results are shown in Figures 10-15. Here, SS runoff rate c is the

0.15

Fly ash Co= 0 .1 1 g/I

CI

0.10

(-)

0.05

0 0 0.5 1.0 1.5 (x6)2.0

V, (m/s)

Figure 10. Fly ash, C = 0.1,1 g/9 0

61

0

. . . . . . . . . . .
(xi 0-)

15

Fly ash C. 10O9/1

10 Ct

5

V. (mis)

Figure 11. Fly ash, C = 10 g/2.

15

Fly ash Co=100 g/1

10- Ct

U

Vo (m/s)

Figure 12. Fly ash, C 100 g/Z 0

62
K. clay Co=0.1.1 gil 1

0.10

C,

0.05 C

0 0.5 1.0 1.5 (xl10 5) 2.0

V. (m/S)

Figure 13. Kibushi clay, Co 0.1,1 g/t

15.

K.clay Co 10 9A

10-

5 C

V. (mis)

Figure 14. Kibushi- clay, C.= 10 g/l.

63
1.15

K. clay C*=100 g/I

0.10

0

0.05

-CA

0 0.5 1.0 1.5 (xO-5 ) 2.0

Vo (m/s)

* Figure 15. Kibushi clay, C W 100 g/t o

ratio of the effluent concentration C and the influent concentration Co, and

the relation to removel ratio r is as follows:

C C c1 r (1)

0

The runoff rate Cq (ideal quiescent) and ct (completely mixing) can be

obtained by following equations:

V

Cq - - fo F(vS)dvs (2)

1 f F(v)• e-"lVod () t S 00

"where

I

V 0 overflow rate, m/sec 0

v = settling velocity of particle, m/sec

F(vs) = cumulative settling velocity distribution

s64
4

"For fly ash, SS runoff rate decreases as the influent concentration increases

as shown in Figures 10-12. For Kibushi clay, the same tendency as fly ash

can be seen for Cq, but act of 100 g/4 C is larger than that of 10 g/4 C

Experimental Parameters and Variables

In these tests, the authors intended to investigate the effect of the

concentration in the slurry influent on that in the effluent, and to compire

the effect of sedimentation promotion vlnong the different layour types of

inlets/outlets, and the effect of sedlmentati,.n promotion by the inr.ýallaLlon

of baffle walls in the containment area. For this reason, only one type of

containment area was used. 'the influent loading time Ot duration was 7 hou.rs

continuously. f

In tests to investigate the relation between the influent concentration

and the effluent concentration, influent concentration was varied from 0.2 to

100 g/v, where overflow rate and solid n..terial were parameters. The. number

of steps of overflow rate was two; soil materials were fly ash and Kibushi

clay. In other tests influent concentration C was i) g/I. o

Water depth of the containment area h did not affect effluent concentration, in tile ideal basin under the conditi ins that the overflow rates were the same among cases and that resuspension if qed mented particle did not occur.

ilowtve r, in preliminary nmodel tests on type A layout (see Figure 21), the efftt

of water depth was observed. When tile water depth ranged from 5 to 20 cm.

thre was no remarkable difference .iamong the 4olids concentration In the efflue'nt, but In the range of 50 to S0 cm, a decrease in concentration was clear.

For this reason and folr convenience of testing. h was set at 10 cm.

Inflient velocity at the end of the intluent loading pipe ,in' was 3

to m/seic in general. In tht-se tests, it was assumed to be ) m/sec. From

thei manab,,ement of water quiality point ,f view, it is reasonable to make

in! lient velocity smaller for reclamation of soft bottom materials. Though

it is not yet clear theoreticalilv how to scale -in in model tests, * caling

was selected using the similarity law of Froude, taking into account descending particles and slurry stream from inlet pipe and density current around

the inlet. As a result of preliminary tests, SS runoff rate decreased abuot

I 32 at 5 cm/sec i"in and increased 'bout 10% at I m/sec "in compare] with

JO cm/sec Vin*

In tihe model test';. Is the influent flowk.d into the containment area,

.i was .ialrready full of tre sh water, itiantit iv ,i! concnt rati.on of the F 1, ,jent varried is ihown in VF',.urn 103. Th). repre.sent atlve vali.z e f S:; con-

. r.tt * it li i ) 0! f lutCIlt was 3i m1.n Value .tft-r the appear:ince of *4teaiv-.state

:I VS : R KS V'. ; S

o! i T :f l u.lt It otuctitt rait ion'

'ler.- were -,)tr• c.i c i in which t he ef f lvint concent. r.ation 'inmc ,ie.ýie.d

l,!,, ll%- thr, i,,,ho,,t ti. tv I1:1i p 'eri d v i',,: lient ,:oncont r.l ion :.' re. ILt ItC . !' i -• - i e - Ii- .tr1 i 'T-. a!h I: ''l O,''4 t f ! ,!

-a,,d - t ltt' ;!'[ Ir' l ;-'t ) q~r',.it {. .,h -iIu - * t . .
600

A type

500. 1

ýz-400

E 300- c. 8000

0200 7000

400

0 6000

100 - . (0 200

0 ''''''0

0 60 120 180 240 300 360

Time (min)

Figure 16. Example of test data

0. 10 500

g -0ý076 10 S0(1 Fly ash Q 5 0.08- /C/: 0S -4000-°'

300 E0.06 300 E

.,0.04 Gq 200 U

0.02: - 100

0 0

0.1 1 10 100

C. (g/1)

Fifure 17. Effluent concentration and

runoff rate, fly ash Q5

0

bb
• " ~~0.2,,.0 0

0. Fly ash 010 1000

800-

015 T 0.1l24.E"10"

600E oIi 4Qoo0*00 , .<o C ( . .) 00°

01 100

Fig~ure 18. Effluent concentration and

run'off rate, fly ash QIO 500

0.20 . * K. clay Q5

0.5 - 400

0.1 " . 3',3000

U I 200

0.05 C

C 200

0 0

0.1 1 10 100

C. (g/1)

Figure 19. Effluent concentration and

runoff rate, Kibushi clay Q5

67

0.1 I I00
-" 0.3,

K. clay Q 10

0.2- '800

U E N T -600

UU

0.1 iL -400

-200

0 0 0.1 1 10 100

Co (gl/)

Figure 20. Effluent concentration and runoff

rate, Kibushi clay Q1O

in the former case, and the -. an steady-state value in the latter case. From

these results, solids runoff ..te C!C0 decreases as the influent concentration C increases, and it c-.., be represented as follows: 0

C/C =aa 1-•l0b (4) 0

where a and b are coefficients that depend on soil materials and overflow rate;

is void ratio and is defined as follows

V - V

S

V

Vs = "sl' (s

C - i 0 s

.. E-=1i-Co/y (5) C0 (5

n-he re

V = volume of influent slurry

V = r."UMU of .;olid particle

= ".-cig t otr : •oI .id p a r t ic l e

68
'I's = weight of solid particles per unit volume

C = solids concentration in influent

On the other hand, effluent concentrat.on C s expressed by the following

formula from Equation 4:

c=C C a E. l ) (6) 0

Equation 6 has a peak value, and the value of C increases until a certain

* point u& Co and then decreases with the increase of C. as shown in Figures 17-

20. Test results showed a larger value of C than the value from Equation 6

in the range of Co larger than the value at which C showed peak value, but

those values are less than or equal to the peIk C value.

For fly ash, the value of coefficient a Is 0.076 and 0.124 at influent

loading rate Q5 and QI0, respectively, and coefficient b is 80 in both kases.

Equation 6 follows well the value-, of C obtaihed by tests in the range of Co

less than 20 g/., but after that it gives les' value than the value of tests.

I'his is especially true for QI0, where the water path varied greatly with the

progress of reclamation; therefore, solids copcentration in the effluent

varied greatly.

For Kibu•hi clay, the value of coefficiei-: a is 0.143 and 0.262, respectively, and b is 160 in both cases. Model tegir became unstable from the viewpoint of reappearance and the test ros, -4%'red from Equations 4 and 6

when CO was approxir.itely 2 g/(.. obtained by the tests was

. •ireater than the vaiue from EquaL1on 6 in the. rE Ye of greater Co, as in the

case of fly ash, hut the difference was smal.i V .. an chat for fly ash and it

* decreased with the progruss uf reclamation.

Upon .cimpariny these results with the SS! runoff rate calculated from the @1 settling vel.,city distribution by settling column tests, several items became

clear. For fl,' ash, SS cunu;cntration in ..f:lhent of model tests is near the

value of ct in the r i.:,<e 'L CO less than I g/A (but the value is greater than

ct in the range ot . 0 gr(aLer than 1U g/IL). For Kibushi clay, almost

the same tendency can 6*w soen, hut only for 100 g' Z CU is the calculated

__ value of c. very vlargv and 'ecmes l:irger thanf the test resulLS.

Comparison ,among Inlet/OutletLavout .vpes

Sedimentation promotion effect by inlet/outlet livout and those structure

types were compared bI SS: ruiuf: rate in the effl,-nt . Each la~cut t~pe is

siion in Figure 21 and their sitructure is show ia Figure 22. Topract c!

• ones can be seen among these typeuz;, but .iivey 'tere id-pted F a r ouar aoses o,

parison. As for the inlet, t'.pe I is one in Wiici, tioe pipe is closed it the

end and cut at the 'Ipr part. In tLip,• L, the pipe is set ,h~nward ml :ne

influent is con',erL,. to radi il directt,-n iv a bai •-, "late i, catd under

pipe. In typo K, ti'e inl'r pipe is sporc d at ti,_ bOtt"tm Of the ris

otlh r types the inlet ,'ipu ti supported at ,:.. ,,t,-r ur!,ici,. A:; fOr ::'W

• 0

ef-iuent weir, . if t, c .... -- dikeo ' r 1,'.J 6- otC:rs ate retaoc'i 1 ,r ,,

Tm, t rtesults arc *;hn ia ,:;,2

0'6
00

4JI

ox In

(\J J

a NN

cn

- I I

cno

70.
0.15

0OA v E

06B G

0 c *i

0.10

001

0-5 1-01.5

Vo (m/s) (x10O

*Figure 23. Test results

015

-F 'L0

o others

* 0.101

00

0 05 10 15

Vo (m/s) (X 0-1)

Figure 24. Test results

71
p.

a.-

In type A, the inlet and outlet aligns in longitudinal direction, and the

-• tested value of c is a little higher than Cq at Q1O, nearly equal to c. at Q5

V" and Q2, and at Ql c is almost the same as c at Q2. In type B, the inlet

and outlet are set parallel but so close that effluent SS concentration is

I• high and near to the value of ct. Type C also has parallel layout but the

*" distance between inlet and outlet is so long that the effluent SS concentration is generally near to cq. Type D has a longitudinally aligned layout, b-t

as the sidewall behaves as a training dike because the inlet is close to t!..

wall, effluent SS concentration is higher than that of A. Type E has _ateral

confrontation layout so SS runoff rate is the highest in all test ca'-> and a

significant difference can be recognized between Q1 and Q2 as in clhe case of

type B. Type F is one of the popular layouts, but test results -. ,owed it to

be less effective than type A. Type G has a longitudinal backward layout of

inlet and outlet, which is easy to adopt when a floater inlct pipe is used.

This type is classified in the least SS runoff rate group. Type H- has a

cross-diked weir and is more effective than type A, and its runoff rate is a

little less than cq. Types J and L have modified inlet pipes and almost the

same results were obtained for both types. The SS runoff rates were slightly

less than cq, and the difference between rate of i ifluent Q1 and Q2 was little.

Type K has an inlet pipe located at the bottom of the containment area.

p Though some difficulties may appear in practical application, this is one of

the most effective types and the runoff rate of this type is less than c q

I q

Summarizing the above, types G, J, K, and L can be said to have high SS

removal effect; types B, D, E, and F have low SS removal effect; and types A,

C, and H exist between the above two groups. Generally, the type in which the

velocity around the inlet is low or Lhe flow path is wide has high SS removal

* effect and the type in which the Aistance between inlet and outlet is short

has low SS removal effect. As the layout of inlet and outlet is often

restricted in the field, type C and G are the ideal cases. Type K is not

suitable for bottom material containing sand and graval. Type J is simple in

structure and is one of the most applicable types in the field.

"Comparison Among Installation of Baffle Walls

The removal effect of the settling basin which has baffle walls or a'

submerged cross dike is compared in this section. Figures 25 and 26 show

layout and structure of these types. 1 is a _ateral cross submerged dike,

2)is a baffle wall of steel sheetpile, and is a floating curtain with a

length half the water depth. Figures 27 and 28 show the test results.

3

Type b has one submerged cross dike 1 . The SS runoff rate of this

t,;e was lower than cq at high overflow rate of O10 and Q5, and this type was

on,1 O) the most eitective. But at Q1 and Q2, SS runoff rate was close to c

and a remarkable difference between type A was not observed. Type c has q

double submersed cross dikes and a little better SS removal effect than

Qb. t '[pe d has five baffle walls of Q in a line. The result of this

tyvpe is near to in the whole range of overflow rate and better than tvpe A

at ov.r!'low rate 1I1!C. Type e has double lines of baffle walls of the d type.

I'ha SS removal ef:ect of it was lower than c and better than type d.

q

72

4
oEl

0l I

C\J 4

U, '0<

C~J ccJ

ol: Sosz= q

U7
0.10

OA 0 k

Ad others c

0.51 1+ .

Va (mis) (x105I)

Figure 27. Test results

ý00V

o c g

/o/

V0 (mf (1

Fiur11.Tstrsut

S(

C0

S0

f 74

S ,Q 2 Q J
i \ I

/

Type f has baffle walls like type d but the walls' location is close to the

"inlet pipe. This type was more effective than type d and as effective as

type e. Type g has one row of baffle walls at the front of the effluent weir

and one row as in type f. When compared with type f, type g does not have a

significant difference. Type h has only one baffle wall of 2 in front of

the inlet pipe. The SS runoff rate of h at QI0 and Q5 was lower than cq,

and therefore more effective than type A. Type h has higher SS removal

ability than type d, which has a row of five baffle walls of 2, and was as

effective as types e, f, and g. Type i has an added cross weir of i added

to type h, and it was a lit le more effective than type h. Type k has

three rows of curtains of 3). and SS runoff rate is lower than cq at Q1O and

"Q5 and more effective than type A.

In this series, there were many types which were effective in SS removal.

The types which have submerged cross dikes (b and c) are effective especially

when overflow rate is large. Among the simple types in structure, type h, f,

and k are effective.

In summary, the types where the flow of influent was decreased or the

velocity of flow was averaged had a better SS removal effect in large overflow rates. There were several types which are more effective than the

types in the former series, but among them there was not much significant

difference in removal effect in the low range of overflow rate like Qi and

Q2. On the other hand, it was remarkable that the less effective types of

B and E in the preceding series had a clear difference in the removal effect

oýwing to the overflow rate, even for small overflow rates.

CONCLUSIONS

Model tests were conducted on the influence of the SS concentration in

the influent on that in the effluent; on the sedimentation promotion effect of

inlett'outlet layout types; and on the sedimentation promotion effect of installation of baffle walls in the diked containment area. Tests were carried out

using fly ash and Kibushi clay as testing materials. Test data were obtained

on =20 cases in the first series, =30 cases in the second series, and =30 cases

in the third series. These data were analyzed mainly by comparing them with

an ideal settling basin. The following conclusions were obtained.

Influence of Influent SS Concentration

Quiescent Settling Characteristics of Testing Materials

Both testing materials showed line settling in the slurry with more than

"10 g/Z solids concentration. The SS concentration of the clear water above

the boundary increased with the increase of the initial solids concentration

in the slurry less than 10 g/Z, whereas it decreased with the increa3e of

initial solids concentration more than 10 g/Z.

As for the settling velocity distribution, the initial solids concentraLio, of less than 1 g/Z did not affect the cumulative settling velocity

distribution. For fly asn, settling velocity became higher apparently in

75

/
p..

the range of slurry concentration which represents line settling. For

Kibushi clay, a similar tendency can be observed, but at 100 g/. slurry

concentration, line settling velocity became low.

SS Concentration in Effluent 7

The SS runoff rate decreased with the increase of influent SS concentration in both testing materials, and an experimental equation, which was a function of void ratio, was obtained. Effluent SS concentration is given by the

product of SS runoff rate and influent SS concentration, and becomes maximum

at around 10 g/Z slurry SS concentration. In the range higher than 10 g/Z,

the experimental value of effluent SS concentration tends to be higher than the

value calculated from the experimental equation, but the value is less than the

maximum value of the experimental equation.

Inlet/Outlet Layouts

Types G, J, K, and L have a high SS removal effect; types B, D, E, and F

have a low SS removal effect; and types A, C, and H are between the two

groups. The type in which the velocity around the inlet pipe is low or the flow

path is wide has a high SS removal effect and the type in which the distance

between inlet and outlet is short has a low SS removal effect. Though the layout of inlet and outlet is often restricted in the field, type J is simple in

structure and is one of the most applicable types in the field.

Installation of ýaffle Walls

There are many types which are effective in SS removal. Types b and c,

which have submerged dikes, are effective when overflow rate is large.. Types h,

f, and k are simple in structure and effective. These types are effective in

the range of large overflow rate. It can be said that such types where the

flow of influent is decreased around the inlet or the velocity of the flow in

the containment area is averaged have a high SS removal effect.

COMMENTS

It was verified that, if the distance between inlet and outlet is short,

particle removal effect is detrimental, not only in the range of large overflow

rate, but also in the range of small overflow rate. On the other hand, the

difference of removal effect is large among the types that are effective in

the range of large overflow rate; for example, the cross dike is one of the

most effective types. But these types do not have significant differences

from each other and are not as effective in the small overflow rates. For

this reason, it is important to consider the overflow rate in reclamation

works, and the decision should be made considering cost performance and

reclamation area utilization if solids removal promotion is needed.

From now on, the relationship between settling characteristics in the

test column and SS runoff rate, and the influence of the process of reclamation on particle sedimentation, will be investigated and the collection of

field data and the study of mathematical simulation will be conducted.

76
REFERENCES

1. Camp, T. R. Sedimentation and the design of settliig tanks, Transaction,

ASCE, Vol 11, No. 2285, 1946, pp 895-923.

2. Clements, M. S. Velocity variations in rectangular scdimentation tanks,

Proc. Instn. Civil Engrs., Vol 34, June 1966, pp 171-200.

3. Cordoba-Molina, J. F. Settling in continuous sedimentation tanks, ASCE,

Vol 104, No. EE6, Dec 1978, pp 1263-1275.

4. Y. Nakazono, et al. Management of waste way effluents containing harmful

matters-PCB and PO 4-P-, Environmental Research in Japan, 1978.

5. T. Yoshida, Principle design of settling basin for reclamation, Hedoro,

No. 3, 1975, pp 4-'.

6. K. Nikaido, Water treatment facility in dredge and reclamation works and

its minimization (1), Environmental Conservation Engineering, Vol 8, No. 1,

1979, p 67.

7. Y. Shiratori, and K. Masuda. Model tests on sedimentation of dredged

material in reclamation ponds (Part-i), Technical Note of P.H.R.I.,

No. 340, June 1980.

8. Thompson, D. M. Scaling laws for continuous flow sedimentation in rectangular tanks, Proc. Instn. Civil Engrs., Vol 43, July 1969, pp 453-461.

9. Discussion, Pro-. Instn. Civil 'Engrs., Vol 46, July 1970, pp 387-393.

10. Y. Shiratori, H. Kato, K. Masuda, and S. Yamauchi. Reclamation with soft

sea bottom sediments, Environmental Research in Japan, 1979.

11. Y. Shiratori, K. Masuda, H. Kato, and S. Yamauchi. Model tests on sedimentation of dredged materials in reclamation ponds (Part-2), Technical

Note of P.H.R.I., No. 388, Sept 1981.

12. Y. Shiratoti, H. Kato, K.. Masuda, and S. Yamauchi. Reclamation with soft

sea bottom sediments, Environmental Research in Japan, 1930.

13. Service water and waste water hand book editorial committee, Service

water and waste water hand book, Maruzen Co., 1978, p 168.

77
4

CAPPING OF DREDGED MATERIAL DISPOSAL MANAGEMENT

"FOR NEW YORK HARBOR

J. M. Mansky

U. S. Army Engi:eer District, New York

Regulatory Branch

26 Federal Plaza

New York, NY 10278

"ABSTRALr

The results of monitoring studies conducted on a

capped mound of dredged material in the New York

Bight are presented. Studies consisted of: a

comparisoa1 of the physical and chemical characteristics of the sediment dredged from each

project, an evaluation of the short- and

long-term stability of the cap, and an investigation to quantify contaminant release through

the cap using biological monitors. Study results indicate that capping of contaminated

sediments is a feasible mitigation measure. In

addition, information is presented on a proposed

study to investigate the use of depressions in

the bottom of the harbor formed by sand mining

for the disposal of dredged material with subsequent capping.

INTRODUCTION

Two previous papers (1,2) presented at the Sixth and Seventh Joint U.S./

Japan Experts Meeting on the Disposal of Toxic lediments have explained the

background of the sediment contamnation problem which was identified in New

York Harbor in 1979, and the subsequent capping of this dredged material in

-- the Atlantic Ocean. A series of investigations were initiated to determine

the effectiveness of the capping operation. Two major concerns were addressed

by the investigations: first, the physical stability of the capped mound and,

second, the effectiveness of the cap to seal off the contaminated material

from the overlying marine ecosystem. It is the purpose of the first section

of this paper to present information in the res Its of monitoring experiments

conducted at the capping site. The second section of this paper concerns

47
investigation of the use of subaqueous borrow pits for the disposal of dredged

material.

CHEMICAL SIGNATURE

The capping experiment at the Mud Dump Site involved the disposal of

sediment from ten dredgiag projects (Table 1) conducted throughout New York

Harbor (Figure 1). In order .o evaluate chemical and physical differer.ces

between each project's sediment and the chemical effectiveness of capping that

material, the Chemical Signature Study was initiated. This study was funded

by the New York District (Corps of Engineers) and conducted by the Institute

of Environmental Medicine of the New York University Medical Center; Dr. Joseph

M. O'Connor was project manager.

To obtain representative samples of the sediment from each project,

individual samples were taken from barges filled with dredged material fro*

each project. In this way, samples were obtained which represented both the

horizontal and vertical variation of the area dredged. Due to the difference

in the volume of the material removed' from each project, the number of samples

obtained for each dredged area varied greatly. For projects writh large numbers

of samples, up to 1S were selected to represent the entire project.

Sediment cores were taken on two occasions at the Mud Duap Site after

(apping was completed in November 1980. On 11 December 1980, gravity cores

were taken throughout the 9ud Dump Site. Coring conducted on 22 August 1981

ionsisted of vibracores taken in the southeast quadrant of the Mud Dump Site

on and ad jacent to the capped mound.

Represent.ative sediment samples from the barges and the cores were

analyzed' for their physical properties, including: water content; grain size;

organic carbon and radionuclides; metals including cadmium, copper, lead, zinc,

and mercury; chemical oxygen demand; and organics including PCB, pesticides,

PAH, and aliphatics (3).

Interproject comparison of the barge samples revealed Chat the sediment

from Ambrose Channel was unique in that all other projects had less sand, more

silt and clay, more water, and more organic matter. Intercomparison of the

other projects revealed that, for individual parameters, groupings of projects

could be made that had similar valijes. Only one project, Jackson Engineering,

could be identified as "unique" due to its extremely high levels of copper,

zin'c, and lead. Generally, intravronect variation, was great enough to obscure

chemical or physical differences between projects.

Chemical and physical analysis of the core samples indicated distinct

sediment layers in some cases. At the capping site, sand was found in varying

thicknesses in the top layer. X-radiographic data of the cores taken in

August 1981 indicated that the sediments possessed a surface layer of sand

ranging from 0.24 to 1.58 meters in thickness (Bokuniewicz, unpublished data).

The average thickness of the sand layer was 1.08 meters.

Inclusion of the dredged material from the Bronx River and Westchester

Creek as part of the cap complicated the discrimination of that material.

I7

S7')
0 unI 1 : o L

-2 'o C.4 .o

0 -~-t u 0 C-'4 ý4 -T ~4~

-~-29

o4 lo

Q. ci to-

- '13

0 ~ ~ to- CA -I~

*~1 7 x' 

li .. Ll0 cc Dt V). -

An en - a, 
L' * ..

. 1

A- - -

4 - '. , , % ,

i-f • ' < - ", "*"--i . , ',, •.•::7.-: ,\ S,-. , "

- , i . , ) k , *. C

5 .,_ • L . . - . . . ., . S

Ii ' -- " '' 

....

0] - . , -- ,. .. . .

SI

Figure 1. Location of dredlging projects involved in capping experiment

e

08
"Although bioassay and bioaccumulation testing (1) indicated that these two

projects were not toxic and showed no unacceptable bioaccumulation potential,

chemical analysis of the sediment indicated that, for the parameters evaluated,

no significant difference existed when compared to the dredged material which

was capped.

The biggest problem encountered in evaluating samples from the material

capped was that in addition to there being a great deal of intraproject variation, many of the projects were disposed at the same location concurrently.

This reduced the possibility of detecting distinct sediment layers for each

project. However, chemical analysis of a portion of a core obtained in

December 1980 did reveal an area which exhibited the chemistry of the material

dredged from Jackson Engineering.

"Connor (3) concluded that, for dredged material contaminated with metals,

SPCB, F d, and/or other organic contaminants, the placement of a sand cap is a

reason ble mitigation measure. A permanent sand barrier would increase the

distz -e between the overlaying seawater and the contaminated fine-grained

sedi,,ent and reduce the potential for resuspension of this material.

SEDIMENT TRANSPORT

One of the assumptions made prior to conducting the capping experiment at

the Mud Dump was that the sand cap would remain in place. Previous research

has been (onducted with a mound of dredged material in the northwest corner of

the Mud Dump to ascertain the quantity of sediment movement from the site.

Freeland and Merrill (4) and Freeland et al. (5) examined dredged material

disposal volumes for the period 1936 to 1973. They determined that 87% of the

volume disposed was accounted for at the Mud Dump. Utilizing the same data,

Dayal et al. (6) calculated the dry mass of material disposed, assuming an

average dry density. They determined that, on a dry mass basis, 82% of the

dredged material could be accounted for. However, using disposal records for

the period 1973 to 1978 for which the data are more accurate, the dry mass

of material disposed which can he accounted for approaches 98%.

To verify this observation for the capped mound, the Atlantic Oceanographic and Meterological Laboratories of the National Oceatiic and Atmospheric

Administration (AOML/NOAA) with funding support from the New York District

conducted the Sediment Transport Study. This study was undertaken to determine:

(a) changes to the cap as a result of bottom currents and sediment transport

over the winter of 1980-1981; (b) the bottom current velocities necessary to

initiate erosion of the cap; arid (c) the long-term probability of erosion by

wind-generated waves.

Two cruises were conducted, November 1980 and June 1981, to collect field

data at the Mud Dump. Sidescan scnar (sonographs) of the bottom microtopography and surficial sediment samples were obtained. In addition, the New

York District conducted bathymetric surveys of the capping area upon completion

of capping, and six months and one year postcapping.

Analysis of these data by AOML/NOAA (7) indicated that the cap showed

82
only a slight decrease in grain size. Nicrotopography data indicated that

sediment transport had resulted in smoothing out the bottom roughness which

will tend to inhibit further erosion. It is likely that some of the sand cap

was eroded and replaced by fine-grained sediment from elsewhere in the Mud

Dump. This intermixing of grain sizes results in poorer sorting and a reduction of mean size which tends to extend cap life. The slight amount of erosion

indicated by comparison of bathymetric surveys was less than the margin of

survey error. Inherent in this comparison calculation is the determination of

accurate figures for quantity of dredged material in-place at the disposal

site upon completion of capping. Tavolaro (8), using a dry mass balance

approach, determined a sediment budget in order to identify and 4 uantify

"losses" of dredged material from the time it is dredged to the time it is in

place at the disposal site. Tavolaro concluded, that approximately 2.0% of

the dry mass measured in-place at the dredging site is unaccounted for in the

barges and was assumed to have been "lost" during dredging. Approximately

3.7% of the dry mass measured in the barges was unaccounted for at the Mud

Dump and was assumed to have been "lost" during disposal.

Field experiments to determine the threshold current velocity, needed to

initiate resuspension of the cap were accomplished utilizing a seagoing flume

(Seaflume). The Seaflume photographically recorded bottom sediment response

to 4 systematic increase in flow velocity generated by a self-contained submersible pump and motor assembly. The Seaflume was deployed in 12 locations

on the capping area. Freeland et al. (7) found that threshold shear velocities at the seabed interface ranged between 0.6 to 1.4 cm/sec, with erosional

current velocities 100 cm above the seabed from 14 to 31 cm/sec. To determine

the frequency of events which would generate sufficient shear velocity to

erode the cap, two investigations were conducted. During the November 1980

cruise two concentration-velocity (CV) probes were deployed on the capping

area to measure currents and suspended sediment concentrations. The CV probes

remained on the bottom, recording data until June 1981. The CV probes consisted of microprocessor controlled electromagnetic current meters coupled

with an optical transmissometer for turbidity measurements, mounted together

on a tripod (7). Calculations of suspended matter concentrations were compli-'

cated by continued dredged material disposal 1.5 kilometers to the: north and

sewage sludge disposal 10 kilometers to the east. Freeland et al. (7) found

that the mean currents 100 cm above the bottom were generally on the order of

6 to 7 cm/sec, with a net direction to the south.

Freeland et al. (7) used wave hindcasting involving the wave spectral

model and the wave parametric model to calculate the hydraulic climate at the

Mud Dump. The first model was based on the integration of the wave energy

balance equation while the second assumed an approximate invariance (9) of the

normalized wave spectral shape with fetch.

Freeland et al. (7) extrapolated existing wind and wave data from the

area around the New York Bight Apex to the Mud Dump. By comparing these data

with that obtained from the CV probes, they determined that the measure of

wave energy shows a strong correlation with turbidity. However, the wave

period does not correlate with the wave energy or bottom current velocity.

rhe depth of the capping site dampens the energy of surface waves and only

the larger waves propagate to the bottom. In conclusion, Freeland :t al. (7)

83
0

determined that wave hindcasting adequately outlines the impact of surface

wa e climate on bottom sediments but it also shows that not all bottom wave

energy is generated locally. Freeland et al. (7) suggested that under longterm averaged waves and currents, little change in cap thickness would occur

after 100 moderately energetic transport events. Swell waves generated by

hurricanes are capable of producing wave heights reaching 13.5 meters (7).

However, storms of this magnitude are not numerous enough to warrant probability analyses.

BIGACCUMUJLATION MONITORING

A basic premise of the capping of contaminated dredged material is that,

to be effective, the cap must seal off the contamination present from the

surrounding environment. To determine the success of the cap placed in the

Mud Dump, it was decided to utilize a biological monitor to quantify contaminant release. The blue mussel, Mytilus edulis, is recognized as a suitable

organism for monitoring coastal pollution in the International Mussel Watch

(10) and has been previously used by the New England Division of the Corps of

Engineers to monitor contaminant release from a capping experiment in Long

Island Sound (11). Under contract to the New York District, investigators

representing the New Jersey Marine Sciences Consortium conducted a one year

biomonitoring study of adult blue mussels transplanted to selected stations

within the New York Bight Apex. Reference stations were selected to quantify

contaminant impacts to the capping area originating from outside sources such

as the Hudson River and sewage sludge disposal. Control stations were established outside known sources of pollution, first along the southern coast of

Long Island and later along the east coast of New Jersey. To determine the

biological impact of disposed dredged material, one station was placed on an

uncapped mound of dredged material in the Mud Dump Site formed since 1914.

Another station was established on the capping site upon completion of disposal of the cap.

The mussels were deployed in twelve mesh bags (100 per bag) suspended

I meter above the bottom from platforms (Figure 2). Initial deployment was

made in August 1980. Premature loss of mussel platforms occurred at three of

the six August deployment stations. The destroyed control station was relocated and a new platform was deployed at the same time the station was established on the capping site, January 1981. One bag of mussels from each platform was collected weekly for the first month and thereafter bimonthly.

Mussels were checked for survival rate and bioaccumulation of mercury, cadmium, lead, PCB, DDT, and petroleum hydrocarbons (as represented by No. 2 fuel

*I oil) (12). Mortality data for the experiment were invalidated due to an

uunexplained survival of only 54% of the mussels after one week at the control

site. A bag retrieved later at the same control site did, however, have a

survival rate of 90%.

Prior to the deployment of the platforms, tissue analyses were conducted

* on a representative subsample of the mussel stock to ensure that the mussels

were not contaminated. A slight elevation of lead (0.83 ppm) was the only

contamination noted.

I

• 34
8.

I..

-SURFACE MARKER BUOY

BREAK AWAY LINE

1 METER

MUSSEL

BUNDLES

MOUNTS

SONAR

... . PNGER

-& ANCHORING PODS

Figure 2. Mussel incubation platform

85

°.
Bioaccumulation of metals was very erratic for the first 5 to 7 weeks.

*[ By the tenth week, differences between stations could be noted and generally

. the plateau level had been reached. Regression analysis of the data indicated

that, in all case-z, the highest value was found at the uncapped mound of sediment existing in the northwest corner of the Mud Dump (Mean values in ppm;

Hg 0.242, Cd 0.081, and Pb 1.13). The next highest mean values were found

at reference stations I to 2 kilometers from the Mud Dump. Mean bioaccumula-

*" tion values for metals at the capping site were quite low for mercury and

"" cadmium (0.030 and 0.041, respectively) while lead was not statistically different than the uncapped mound value at 1.04 ppm.

PCB bioaccumulation showed wide fluctuations throughout the study. No

". conclusions could be drawn from the results as to the source of PCB or the

reason for the fluctuations in values. PCB bioaccumulation in this study

could not be correlated with mussel lipids, in deference to the propensity of

data indicating a positive correlation.

Bioaccumulation values for DDT were generally below detection for mussels

from all stations. This finding corresponds'to the lack of statistically

significant bioaccumulation of DDT for any sediment proposed for ocean disposal within the New York Harbor Area.

Results of No. 2 fuel bioaccumulation over time indicatel that after a

"" minimal accumulation in the first four weeks of exposure, no further change

was detected until there was a dramatic increase in late spring. The pattern,

of mean values of No. 2 fuel oil concentration was generally the inverse of

the pattern shown for metals concentration. Mean fuel oil concentration at

the capping site (0.667 ppm) was greater than that for the uncapped mound 1 (0.20 ppm) and all other reference stations.

Koepp et al. (12) concluded from this study that: (a) mussel survival

and lipid content did not statistically correlate with bioaccumulation of any

contaminant for any given station; and (b) the absence of ancillary contaminant

data for sediment, water, and mussel food restricted the extent to which the

observed contaminant accumulations can be more specifically related to dredged

material disposal.

SUBAQUEOUS BORROW PITS

- Subaqueous borrow pits are irregularly shaped depressions on the sea

floor caused by sand and gravel mining, typically for construction material

"* and beach replenishment. In an area within 160 kilometers of New York City,

the demand for this material has been predicted to be about 10 million cubic

meters per vear (13). Most sand mining in the New York Harbor area is confined to the Lower Bay which is composed primarily of sand and gravel (14).

The volume of existing borrow pits in the Lower Bay is about 23 million

cubic meters (15). The idea of using borrow pits as containment sites for

dredged material is not new. It was suggested as early as 1973 by Carpenter

"* (16). Technology is available to carry out a disposal operation over a

borrow pit. Volume I of the Mitre Report (17) identified the use of subaqueous

borrow pits as feasible for large volumes of dredged material and a possible

option for disposal of contaminated dredged material.

86

4.
"The filling of borrow pits is an environmentally beneficial dredged

material disposal option since borrow pits are known to be subject to a high

"I rate of fine-grained organic sediment deposition, with attendant adverse

"environmental impacts (18, 19, 20). When disposal of fine-grained dredged

material is combined with the placement of a layer of sand as a cap, the area

can be restored to its original condition and productivity of the area should

increase. The filling of borrow pits with fine-grained dredged material does

have the unavoidable consequence of removing that immediate area from any

"future sand mining operation.

In order to evaluate subaqueous borrow pits as a dredged material disposal

option, the New York District initiated a contract with the Marine Science

Research Center at the State University of'New York at Stcny Brook (MSRC).

MSRC had previously spent several years investigating the environmental effects

of sand mining and filling of the borrow pits within the Lower Bay. Model

studies were conducted and the results evaluated. It was determined that a

5demonstration project was required to obtain further information on the

feasibility of combining the two operations.

Site selection consisted of an evaluation of the following factors:

1. Site must be accessible to barges for the disposal operation.

2. Site must be such that the pit is deep and large enough to contain the spread of the dredged material when it encounters the bottom.

3. Site must be outside areas susceptible to high wave and current

energies.

4. Site must not be an area of high biological productivity.

5. Site must not be an area of current sand mining operation.

Evaluation of the above criteria revealed that no currently existing

borrow pit was totally acceptable. Investigation was made of the idea of

creating a borrow pit of ideal dimensions in an ideal location. This idea

was dismissed because of the high cost and the disruption of an undisturbed

area. It was determined that the best option available was to modify an

existing borrow pit.

* A borrow pit located in the center of the Lower Bay was chosen as the

site for the Demonstration Project (Figure 3). The purpose of the Demonstration Project was to assess the physical stability and technical feasibility

"of capping dredged material within a subaqueous borrow pit. This borrow pit

was originally dredged in the early 1970's to a depth of 28 meters below mean

low water. Since that time, approximately 3.8 million cubic meters of dredged

4 material has been disposed there, in an effort to alleviate the anoxic condition present in the bottom of the pit. Schwartz and Brinkhuis (21) have

"documented that a high r3te of natural sediment deposition, low dissolved

"oxygen, and impoverished benthic fauna exist at this borrow pit. The sedimentation rate in the pit (on the order of 10 centimeters/year) was reported to

be 100 times that of natural sedimentation rates in other estuaries, while no

87

I-
6f

2~ . ('K LONG

= ~ . A :-*.~ISLAND

* ~ ,r. ISLAND *.

35'

%,%

---

• -. V & 

"PROPOSED

,.IAREA V DISPOSAL

40030'

- .

.

. ... " ' 

-' "- i"---." . • . - .." -. • -, ._. . . "- •. --

35' " f• . ",..... .

25'

NEW JERSEY

'Pi

. . • • ---. I . . * .

3; ;

20' - .. V

15 10' 74000'455

Figure 3. Site location of bor, w pit to be used for Demonstration Project

88

* * 

/ -. '
sediment was found to be accumulating on the shallower sandy bottom surrounding

the pit. Due to the organic fraction of the sediment which exerts a high biological oxygen demand and has certain contaminants chemically bound to it, the

borrow pit supports a benthic community of about 137 organisms per square meter

while the surrounding area supports about 1100 organismL per square meter (15).

Because the remaining capacity of the borrow pit, 3.8 million cubic meters,

was determined to be too large, it was decided to conduct the project in three

phases. As proposed, phase I (Figure 4) of the Demonstration Project would involve the disposal of approximately 153,000 cubic meters oi sand. The disposal

of this material would accomplish two objectives. First, it would be used to

determine the energy' of the surge ot the dredged material once it hits the pit

bottom. Second, the material would be disposed so that it would form a threemeter-high berm across the southern portion of the borrow pit to create an

isolated pocket consisting of 10 to 15 percent of the volume of the entire

pit.

Phase' II of the project would consist of the disposal of approximately

300,000 cubic meters of fine-graiied sediment. This material would be nontoxic and uncontaminated sediment as demonstrated by bioassay and bioaccumulation testing. The phase II sediment would be placed behind the berm.

Phase III.'wculd involve the disposal of 230,000 cubic meters to cap the

tphase II material. This dredged sediment would be non-toxic and have no

unacceptable bioaccumulation potential, and at least the top 0.3 meters would

4 consist of clean sand the same grain size as the surrounding bottom. Upon

completion of phase III, a monitoring program would be initiated to determine

* ."physical and chemical changes to the borrow pit and surrounding area.

During the month of December 1981, 167,000 cubic meters of sand was

dredged from the Federal Navigation Project at Ambrose Channel for construction

of the berm. Disposal was accomplished utilizing the Corps of Engineers hopper

dredge Goethals. This creatcd an isolated area with the dimensions 200 meters

wide by 200 meters long with . maximum depth of 14 meters below mean low water.

Prior to the initiation of phase II, the Water Quality Certification

issued by the New York State Department of Environmental Conservation authorizing the project was challenged in state court by a private environmental

organization. It was the'allegation of the environmental organization that %

the borrow pit proposed for the Demonstration Project was an area of high

biological productivity and, as such, an Environmental Impact Statement should

have been prepared. At this time, the lawsuit has not been resolved. In the

interim, the New York District Corps of Engineers has been funding two studies

to further evaluate the biological productivity of the borrow pit and determine

its relative importance compared to the rest of the harbor. Analysis of the

results of these two studies is anticipated to be completed by the end of

1982.

CONCLUSIONS

In 1980, the New York District conducted a capping experiment to resolve

an urgent need by several permit applicants to dredge sediment which exhibited

89

/ // -, "I
•. °. - *°/

/"

20

20- - I%

40

40

C 13

I.

MAIN SHIP CHANNEL

PROPOSED A 5Q

BERM Y

400

I

20- C 11 -A' I

0' 1800"

PLAN VIEW OF BORROW PIT

-20- -EXISTING BOTTOM

DEPTH, FT _40- . . .. z...z.

S-60 /,

A PHASE I COMPLETION A'

-10,

-20o ......................... ,.....................EXISTING BOTTOM --30 ... """"" "- .•

D E P T H , F T - 3 0 - .. ... - - /

-40 --

-60

A A'

PHASE II AND III COMPLETION A

CROSS SECTION A-A" (1" = 400')

Figure 4. Proposed borrow pit Demonstration Project

9J
a statistically significant 1ioaccumulation of PCB. The capping exercise was

based upon two premises: (1) that the capped mound would be physically stable,

and (2) that the cap would seal off the contaminated material from the marli e

environment. Results of studies presented in this paper indicate that these

premises have been fulfilled.

Currently the New York District is utilizing capping to allow some contaminated dredged material, for which no other disposal option exists, to be

capped in the ocean. In addition, as part of a dredged material disposal

management program, all ocean disposed dreded material is dumped at a tautmoored buoy in the Mud Dump Site. In this way, sediment in need of capping

receives a covering of additional uncontaminated dredged material to further

isolate the contaminated material.

The ultimate solution to the problem of dredged material disposal is to

have a sound manJgement strategy which can clearly predict the most environmentally sound and economically feasible disposal option. A successful investigation of the subaqueous borrow pits would increase the options available for

contaminated dredged material containment. With a variety of disposal options

available, dredging projects can be planned and carried out in a timely fashion

thereby maintaining economic integrity of the Port of New York and New Jersey

while at the same time p-otecting environmental resources.

9,1
REFERENCES

1. Suszkowski, D. J., and J. M. Nansky. "The Disposal of Sediments

Dredged fromi New York Harbor," 6th Anuail US/Japan Experts Meeting on the Disposal of foxic Substances, Tokyo, Japan. 16-18 Feb 1981.

2. Susikowski, D. J. "Studies on Capping oC Contaminated Dredged Material

by the New Y~rk District, Corps of Engineers," 7th Annual US/Japan Experts

Meeting on the Disposal of Toxic Substances, New York, New York. 2-4 Nov 1981.

3. 0' 4Cnnor, J. M.. "Identifying Chemical Signatures for Disposed Dredged

Materials," New York University Medical Center, Institute of Environmental

Medicine 0019$2).

4. Freland, G. L., and G. F. Merrill. "Deposition and Erosion in the

Dredge Spoil and other New York Bight Dumping Areas: Proceedings of the

Spetiality Conference on Dredging and its Envircnmental Effects," American

Society of Civil Engineers. Mobile, Alabama (1976).

5. Freeland, G. L., D. J. Swift, W. L. Stubblefield, and A. E. Cok.

"Surficial S~diments of the NOAA - MESA Study Areas in the New York Bight:

Proceedings o~n the Symposium on the Mliddle Atlantic Continental Shelf ~and The

New York Bijlt," American Society of Limnology and Oceanography. New York,

New York (1976).

6. Day 1, R., Mi. G. Heaton, M1. Fuhrman, And 1. W. Duedall. "A% Ge'ohenical and Sedi'ientological Study of the Dredged Material Deposit in the New York

Bight," NOAAlTechnical Memo. OMPA-3 U.S. Department of Commerce (1981).

7. Freeland, G. L., R. A. Young, G. Drapeau. and T. L. Clarke, "Sediunent

Cap Stability Stud', New York OretI~PO Mate-rial Dumpsite," Draft Report suhmitted to the Now York District Corps ot Engineers by Atlantic Oceanozraphic

Anand Meteorco'log•cal Lahoratorirc,. NOAA. Virginia Key, Miami, Fla. (1982).

8. T,'jolaro, J. F. "Sediment Rudget Study for Clam-shell Dredginp and

Disposal Activities," Draft report ýurrently under review prepared •-v the

New York D4strict Corps of Engineer!, 26 Federal Plaia, New Yjrk, N.;. (19F2).

9. a-s.Ielmann, K., D. B. Hss, P. Miller, and W. Sell. "A Parametric

Wave Prediction Model," Journal of Phys:cal )eanography 6(2): 200-228 k1976).

10. Goldberg, F. E., U. T. Bow.An, J W. Farrington, F. Harvey, .J. H.

* Martin, P. L V Parker, R. W. Risehrtugh, W. Robertson, E. Schneider, and

""E. Gamble. 'The Mussel Wa,(h," Env:ror.mental Conservation 5(2): 101-125

(1918).

11. Feng, S. Y., R. U. Gr .llo, R. Aricoto, j. K. W4tson, F. M. l{a',h1vo,

And T. R. D'i#lette. "Heavy Metal Conce'itrations and Gonidal Development ina

Mytilus modlolus," 0A.MoS Report NAva'l Underater Systems Centtrr (.971),

--- - -
"12. Koepp, S. J., E. D. Santoro, R. Zimmer, J. E. Nadeau, and L. Ciaccio.

"Bioiaccumulation Monitoring in the New York Bight Using the Blue Mussel

(Mytilus edulis)/" New Jersey Marine Sciences Consortium (1982).

13. Courtney, K., J. Dehais, and W. A. Wallace. "The Demand for Construction Minerals in the Greater New York Metropolitan Area," New York Sea

"Grant Report Series, 7q-10 (1979).

14. Jones,'C. R., C. T. Fray, and J. R. Schubel. "Textural Properties

of Surficial Sediments of Lower Bay of New York Harbor," Marine Sciences

Research Center. Special Report 21, New York Sea Grant Institute

Reference 79-4 (1979).

15. Bokuniewicz, H. J. "Progress Report on Study to Use Submarine Borrow

Pits in the Lower Bay as Containment Sites for Contaminated Dredge Sediment,"

17 July 1.981.

16. Carpenter, J. H. "Determining Ultimate Capacity of the Coastal Zone

for Wastewater and Wastewater Residuals," In Ultimate Disposal of Wastewaters

and Their Residuals. F. E. McJunkin and P. A. Visiland (Eds). Water Resources

Research Institute, North Carolina State University, Raleigh, NC: 216-244

(1973).

17. Conner, W. G. Aurand, D. Leslie. H. Slaughter, J. Amr, A. and F. 1.

Ravenscroft. "Disposal of Dredged Material within the New York DistricL.

Present Practices and Candidate Alternatives, Volume I," Report prepared by the

4ITRF Corp. for the New York District, Corps of Engineers (1979).

18. Mkirawski,. 9. "A Study of Submerged Dredge Holes in New Jersey

Estuaries with R-.p, to Their Fitness as Finfish Habitat," Misc. Rpt.

No. 214. New Jerse, 'ftvt. of Conserv. (196Q).

19. Broughton, j, !). "!nvestiatimn of Subaqueous Borrow m its as Poten-

"" tial iitpq for Drerl.'d MjL'.rial DisposAl," Tech. Rpt. 0-77-5. U.S. Army Corps

of EnFgineers, 'W.E.5 Fnvirt,,en,,41 Effects Lab (1977).

20. Taor•n•ina A. '. "o*,41 Management for Resources Values of Long

Island's Tidal w'elud,,.., .eaflet FW-P21. New York State Dept. of Ervirinment.al Conservation ( 1,1).

21. Schwartz, S. It , inti 8 H. Prinkhuis. "The Trpact of Deep Holes on

Oxygen Demand in the Lowr BAy. New York ,i.ur or.' Spec.- Rpt. 17. Marine

Science Research Center, S.U.N.Y. it Stonny Broo, (1978).

'4•

1,

; :.
I

RESTORATION STUDY OF DREDGING

IN LAKE KASUMIGAURA

Fumio Kodama

Director of Kasumigaura Work Office

Ministry of Construction, Japan

Tamiya Fukushima

Head of Investigation Section

Kasumigaura Work Office

Ministry of Construction, Japan

INTRODUCTION

Lake Kasumigaura is the second largest lake in Japan and is eutrophic.

The sediment has adverse effects upon water quality and has a thickness of

about 40 - 50 cm.

In order to remove sediment as a link in the chain of restoration,

dredging is now partly under way. Howeve r, problems remain as to how the

secondary impacts by dredging can be abated and how to manage the dredged

material. An outline of past and future studies of these problems is presented herein.

BACKGROUND

Lake Kasumigaura (Figure 1) is situated in the southeast of Ibaragl

Prefecture, which is located nearly in the center of the east coast of the

Nippon Islands. It connects to the lower part of the Tone River through

Hitachi Tone River and has the second largest *rea in our country with

56 inflowing rivers.

Basin data are presented below:

Basin area 2169 km2

Towns and villages 47 (23 environs of the lake)

Average annual rainfall depth 1350 mm

Average annual rainfall quantities 2.82 x 109 m3

Average annual runoff discharge 1.39 x 10 9M3

Average annual runoff rates 49%

Population 720,000

As the above data show, the basin area of Kasumigaura is 2169 km2

and occupies about 35% of the total area of Ibaragi Prefecture.

94
A)

0 A

~~ ( * AITAS~

Figure 1. Kasumigaura Basin

95
.4f

The average annual rainfa l~depth is about 1350 mm and the total quantity

of inflowing water is 1.4 x 10 m and lake water volume is replaced

"1.7 times/year.

Most parts of basin have a stretch of hills with a height of 20 - 30 m,

or flat land (like rice fields) around the lake, except for several mountains

like Tukuba (876 m) and Kanami (709 m).

There are 56 inflowing rivers such as Onogawa, Sakuragawa, Koisegawa, tiSonobegawa, and Tomoegawa and only one outflowing river, Hitachi Tone.

Hitachi Tone River has a small bed inclination and complicated hydrologic

P... conditions because of the brackishness of the water and the influence of the

water level in the Tone River.

The basin has 47 towns and villages extending over the two Prefectures of

Ibaragi and Chiba and a population of 720,000. Industries in the basin are

mainly primary industries. Among them, two are prominent: hog raising and

carp farming.

The morphometry of the lake is as follows:

Water level Y.P.* + 1.0 m average sea level + 0.16 m

Lake area 220 km2

Coastal line 252 km

Max depth 7 m

Mean depth 4 m

To meet an increasing water demand in the capital city and its environs,

an integrated Kasumigaura development project (Figure 2) is now moving

Planned High Level

Y Y.P. + 2.85m

H i-1 1 Limit V. for I prove rnt

'P + 2 

O m,85m_ 

e cr o r a er V l

,•- •:• Higher Limit -... / -

Levetl e in 3o.39r1 ]x~~

;..- + 

t Re , otal tervWa r Vol.

-imt LI.,ve it ' • - - " " b r _ . ' ýo r ' t l l z - ,

* "K Lwe Dead .- '\Y- Y.P. , imtree ('m "a 27 1 tex ~0 m •1.31

gure 2. Volure ilotmont in Kasur,'igaura

SY.P. =datuir plarn, elevatlon of Ton&, Piver 4orks.

"9')
L

forward in terms of water imnrovement and utilization. It aims to develop

water quantities -f 280 x 10 m , which correspond to the volume between

Y.P. + 1.3 m and Y.P. + 0 m by the project completion year of 1985.

Furthermore, big projects developing the Kashima seaside industrial area

and the Tsukuba research and education zone are promoted along with this water

L. resources de elopment.

The lake water is now maintained as fresh water by use of a backward flow

protecting floodgate, which was built in 1963 for river improvement at the

lower part of the Hitachi Tone River. in this way, Kasutmigaura has become a

large artificial water reservoir. Therefore-, close attention must be paid to

protect its water quality.

OUTLINE OF WATER AND SEDIMENT QUALITIES

The water quality in Kasumigaura has deteriorated in such a way that

oxygen demand (COD) Schemical concentrations, which were about 4 ppm in 1955,

have increased to 7 - 8 ppm in the latter half of 1965 and to 10 ppm after

1978.

The environmental standard for COD for Kasumigaura was designated in 1972

as' 3 ppm considering the water purposes. But as Figure 3 shows, water quality

has become remarkably worse since 1970 and, at the present state, greatly

Sexceeds the guideline.

A r -7 .. 7....... -r .. T J:

6 - -' S'/ . L :~~',., i ---- r0011entLa| :.--.- 1, --- •? •'' L ---- ' t, , -dS[

2 L . . __

•." t967 i VTO 1;75 o

Fi.gure 3. Chanve f,. fit) concnetratr'lns

,\ cotinterne•sures for this wate. dc-terioration, the reguldtiin of

* uttluents was strengthened and sewage ,;v-., ,. werý cousolid!ated. However,

even withi these :measures, the present -t.•. of water quality still teind.s t,

beconre worse.

sn ummer a eutrophication phenorr, - C,,:s in that piytoolao•ton .

by nitrogen and phosphate hreed in K'; ' "-a'.' erp,.rat,.-'., .As th- t.te' 1(,

"7
velocity is low in stagnated water areas such as lakes, most suspended solids

settle to the lake bottom and result in pollution of the sediment.

Polluted sediment adversely impacts upon water quality through the nutrient materials that are released from sediment and eluded from the resuspended

* solids. This is an internal lake pollution load.

In eutrophic lakes like Kasumigaura, phytoplankton are produced by nutrient inputs. Dead matter settles to the lake bottom where it decomposes, and

nutrients are released from sediment, spread up the water body, and help

regenerate plankton.

Since release phenomena are vigorous in high water temperatures, the lake

"experiences blue-green algae blooms in summer. In this way, sediment in

Kasumigaura is degraded similar to water. It spreads in the whole lake accum-

"ulating from several centimeters to scores of centimeters in thickness. I

WATER QUALITY IMPROVEMENT PROJECT IN KASUMIGAURA

Domestic drainage, factory effluents, and rural drainage are considered

as pollution sources. The internal load by released material from sediment is

also presumed to be a cause of pollution.

To meet these problems, dredging commenced in 1975 as a restoration mea-

* sure (supervised by direct national administration for implementing river

environmental improvements).

The quantities of sediment to be removed in Kasumigaura reservoir area

project have been set at 300,000 m by 1981. Dredging is now continuing at

heavily polluted offshore estuarine areas such as Sakuragawa (Tsuchiura City)

and Koisegawa. Table 1 shows the dredging results.

Table 1

* Dredged Volume

3 3

Year Dredged Volume, m Accumulated Volume, m

1975 4,000 4,000

1976 18,000 22,000

1977 13,000 35,000

1978 34,000 69,000

1979 40,000 109,000

1980 85,000 194,000

1981 106,000 300,000

In Kasumigaura the dredge KASUMI (with negative pressure suction) was

developed to prevent secondary impacts from turbidity. An improved dredge

KORYU was put into operation in 1978. Most of the dredged material is

dewatered at management ponds by normal densification methods or by progressive trencning and then used for banking embankments in city public spaces.

In addition to the dredges, a special boat for gathering phytoplankton

was developed and operates during the summer.

98
The local government (Ib.ragi Pref.) issued "the regulations to prevent

eutrophication in Kasumigaura" and enacted the following countermeasures

beginning in September 1982:

(1) Consolidation of sewage systems for domestic drainage and prohibition

of the sale of cleaning agents containing phosphorus.

(2) Strict observation of effluent regulation standards and strengthened

regulation of effluents.

(3) Guidance for correct fertilization to control rural drainage.

(4) Consolidation of domestic animal excreta control facilities for stock

effluents.

(5) Rationalization of carp farming method and change in fish species.

(6) Dredging of inflow'ng rivers and control of aquatic plants.

VACUUM SUCTION AND PNEUMATIC DISCHARGE DREDGING SYSTEM

A dredge with a vacuum suction and pneumatic discharge system was built

in 1978. It has the following features:

(1) Minimal turbidity can be expected.

(2) A swing method is maintained for dredging to increase operational

efficiency.

2 (3) A liquid pressure pump (max pressure 40 kg/cm ) is maintained for

discharging dredged material.

(4) It is equipped with devices for inspecting the excavation and

measuring the sediment volume.

The main data of the dredge are as follows:

Max dvedging depth 7 m

C&nveying distancp 2000 m

Dredging capacity Over 100 m 3/hr (water content

of 2000%)

Diameter of delivery pipe 150 mm

3 Capacity of suction pump 2 x 0.85 m

Vacuum pump 720 m 3/hr, -500 mm Hg

Screw type air compressor 1 x 1200 m3 /hr, 7 kg/cm2

99

- - - - - ---
Working Principle of Vacuum

Suction and Pneumatic Discharge Pump

"The suction head, which consists of two sediment hoppers and a suction

mouth, exhibits suction and discharge actions alternatively by valves such as

suction switch valves, suction valves, and ball valves (Figure 4).

i•: -[-- D~e liver yy ;

I T-• r• -t• Vacuum Pump

' compressor

i " • "Ball Valve,

Hopper

Suction Switch Valvc

Sediment '///z_7, *// ,

Suction Mouth

"Figure 4. Working principle of pump

The vacuum pump acts at a vacuum of -500 mm Hg; when the required quanti-

. ties of dredged materiai are filled into one hopper, the suction process is 9

stopped by the working of the level switches. Then compressed air (7 kg/cm-)

is automatically supplied to the hopper by the air switch-cver valves to push

out the sediment with the help of the ball valves. When the remainder reaches

Ct'e lower limit level, exhausting of sediment is stopped by the working of the

level switches. By repeating these processes through alternative use of the

two hoppers, continuous and smccth dredging is achieved (Figure 5).

•. t 1 I I I Time (sec)

IL

SFigure 5. Diagram of dredging action using alternate htoppers

100

Iu
The Digger and Its Performance

As Figure 6 shows, the digger has an open suction mouth, which is shaped g so as to be able to suck 'sediment continuously by using a swing system.

Suction Monuth

t450 4.500 1 1

Figure 6. Shape of digger

It is known that the share of the suction mouth has a large effect upon

dredging performance regarding sediment disturbances from dredge impact.

'When removing upper sediment layers, it is necessary. to minimize the

intake of water in the sediment surface for efficient removal. This requires

not only a good shape of the suction mouth, but also consideration of various

sediment properties and dredging conditions such as dredging depth and swing

speed. Tests on two kinds of suction mouth shapes were performed concerning

this proLlem.

The relationship between digging height and water content is shown in

Figure 7, using zero height for the contact face of the digger bottom and

sediment. 6

43 30-

0 00

700

go]

1.O000

i0 0 Measured

* Calculated

0 0.5 1.0

Digging Height (m)

Figure 7. Relationship between digging heights and water content

101
4.

At that time swing speed was left to the judgment of the operator to

"maintain smooth dredging. These tests emphasized sediment content over

removal efficiency and the finishing accuracy of the dredged surfaces.

From these data it can be said that:

(1) The sediment content of the surface of the dredged material is about

14%.. This value slightly exceeds 10 - 13% normal in hydraulic dredging.

(2) The deeper the digging depth, the higher the sediment content. For a

digging depth of 0.5 m, sediment content amounts to about 24%.

(3) The finished surface after dredging is rugged and uneven.

(4) A digger with a suction shape is not suitable for superficial sediment removal.

In the next stage an improved digger form was developed as shown in

Figure 8.

;l 960

Sution Mouth

-.O8O mm

Figure 8. Improved digger

The test results demonstrate a good applicability for thin layer

dredging, having the following points:

(1) Sediment content increases according to swing speed, but converges at

some final value. This may result from the fact that some sediment moves away

from the side of the digger (Figure 9).

(2) Removal efficiency decreases according to swing speed. For higher

removal efficiencies, a lower swing speed is desirable. However, doing so

increases water content and lowers removal efficiency (Figure 10).

(3) For an open edge type digger, some water enfolding is unavoidable in

a swing system.

(4) Digger forms have their own performances with variances according to

sediment properties such as viscosity, specific gravity, and sofl strength.

Dredging Operations

During Iredging, the dredge advances with one cut of 1.1 m, striking the

main and auxiliary spuds so that no upper sediment layers remain (Figure 11).

102
25 6.0

0

"5.0

-20

0-o.

• 1 5 4.0 q

S e Content

•N 

4.4

0

Ratio of Sucked

- Sed. Content Water to Sed.

0 Volume 10

2 4 6 a iO 12 14

Swing Speed (m/min)

Figure 9. Relationships between swing speed and sediment content

100j

O..%

9 90 U 80

70. 0.3 M'I • °,• 60

"M 50

r 40 0.5 ,.

30

2 4 6 8 10 12

Swing Speed (n/mm)

Figure 10. Relationship between swing speed and removal efficiency

103

• "'. 2. i,.."2, "."" i '.'. "" • '-... . . .-.. .
Aw Vdt 0 h 40.A

Figure 11. Dredging operation

Two swing speeds are possible, one for d'gging and one for cleaning, to

avoid e~xcess water. As shown in Figure 12, t .e restilts monitored by e-ottnid

* waves indicaite a re1;atlvelv smooth suarfaice with this method.

3m

0.5

2 .)

2 . 5

3. 5

4 4

(80 .

F igu re 12 . S~ed ime ot s urf a c v nn Ior red b v su n (I W.iv
Relation Between Sediment Volume and Discharged Water Quantities

. According to our dredging, experiment the relationship between sediment volume

and discharged water quantity is described by the following formula:

" €1 €2 Sh (1 * a)

where

Q - discharged water quantities. U3

"".1 surplus water efficiency (sucked water eff.), 1.8 - 2.1

Y2 - removal efficiency, 0.8 - 0.9

.ctual dredged quantities

planned quantities

2

S - dredged area, a

h - dredged height. m

a - excess sediment

MANAGEMENT OF DREDGING WORK

Present State of Sediment Pollution

and Its Removal as a Restoration Measure

Dredging is thought to reduce the release ot loads through sediment

removal, which may contribute to improved water quality.

As Figure 13 shows, sediment in Kasumigaura is polluced to a large extent

in its upper layers with little pollution occurring in lover ones. An

exponential relationship seems to exist between nutrient concentrations and

release rates. Therefore, if sediment removal from H to H is conducted, the

pollutants in the sediment decrease from C0 to CI an releole rates decrease

from L0 to L 0'

*e Figure 14 shows the vertical distribution of total phosphorus (T-P) in

sediment against sediment depth. From this we can say that, for an effective

improvement of water quality, it is desirable to dredge the widest possible

areA even if only a Small thickness is removed.

Ptirpose and Subject cf Dredging

Dredging r!Arr.-itly under way is aimed at improving water quality. It

differs from maintenance dredging for water depth, or protecting blockades in

estuaries.

105
LL Concentration eNutrient 

nuretcneta Co- ocnrto

tion

Fgr 13 etcldsrbto fnutrient concentrations :'. d son

Nutrtrkaa ien ocn a o

of nutrent Conenorfshoncenrto

Figure 13. Vertical distribution of nutrient concentrations

ar.d releageu rates againgt them

Concentration of T-p

(mg/gT dry sediment)

197t 400 0 * 3 4 m 

i • a Lake

S• Centre ,' Takasaki

S. Offshore

|S.-

Figure 14. Vertical distribution of T-P in sedient

Water quality dredging differs in the foblowing ways:

(1) A snail thickness of sediment may have to be dredged according to

sediment conditions. Water depth is also small.

S~(2) It is difficult to estimate the sediment volume dredged because

sedinent volumes are largely a function of working con~ditions,

ResuJlts of Dredging

The dredged quantities of sediment to .ate are as follows:

41975 4,000

1976 18,000

1977 13,000 m3

lob
31 Lo

ENW R, i MG N

250! iMAXIMUM

'" R OL .fJL A.l P

' _ _C _ _____---__I

Figure 15. General view of the dredge KIRYl"

1978 36,000 3

1979 40,000 N

3 1980 85.000 a

1981 106,000 3

300,000 u

Problems on Work Confirmation

Problems with work are as follows:

(1) Due to the shallow water depth, the guidelines on "sediment quantities" defined by "civil work common specificaklons" cannot be applied.

(2) As the water content of sediment is high and the sediment volume by

working conditions varies greatly, it is difficult to estimate the sediment

volume dredged.

107
(3) Sediment removal in the upper layers must be controlled.

(4) The guidelines for work confirmation are not always clearly defined.

(5) Sediment content changes largely according to dredging operations.

There are four ways to check sediment volume. Measure the discharged

quantities of the delivery pump, estimate planned values, measure the management ponds, and measure transported quantities. These four methods give very

different results. To solve these problems, the investigations discussed in

the following section were conducted.

Checking Dredged Sediment Volume

Dredged sediment volume changes greatly according to water content (Figure 16). In checking this volume, the following conditions should be

considered:

(1) Sediment is at the lake bottom in a state consolidated by natural

accumulation.

(2) In hydraulic dredging, water content becomes high and discharged

liquid quantities large because water is sucked along with sediment.

(3) The water content and sediment volume in dredged material settled in

the management pond vary with rainfall and evaporation.

Three calculations of sediment volume are conventionally conducted:

Sediment Dredged Material

- -- Water Change by

bkq• Rainfall and

Fake Evaporation

ger

-- --"4" in Pond

Dredging

Figure 16. Solid and liquid content of sediment

1 -V1 X 100 + GSW

108
-v•10s "M 2 V2 x 100 + GsW2

M lOOGs

3 3 100 + GsJ 3

uhere

3 V1 = sediment volume at the bottom, m

3 V = discharged water volume, a 2

V = sediment volume in management pond, a 3

M 1 dry weight of sediment at the bottom, tons

M - dry weight of discharged water quantities, tons

M3 - dry weight of sediment settled in the pond, tons

W, - water content at the bottom, Z

W - water content of dredged liquid, 2

W3 a water content in management pond, 2

Gs - specific weight of sediment solid, 'tons/mr3

1

, 109

0.
-°.

The advantages and disadvantages of these calculations are indicated in

"Table 1.

Table 1

Merits and Demerits of Sediment Volume Checking

Merits Demerits

V1 (I) Sediment volume is removed (1) Survey errors are large

from the lake bottom

(2) Sediment volume cannot be

(2) Dredging is conducted estimated before work

generally on the basis of completion

sediment volume at the

bottom (3) It cannot be checked for

progress

(4) In future dredging of sediment with high water contents,

sediment in the already

dredged area may collapse

V (1) it can be taken for sedi- (1) Adjustment with a flowmeter

ment volume, which has is necessary

passed through the delivery

pump (2) Adjustment by measuring

the sediment content is

(2) It is easy to control by necessary

digital displays

(3) Troubles with flowmeters

(3) Control results can be may occur

directly reflected in the

progress

(4) Nec working hours are controlled by charts

(5) Sediment contents are controllable by charts

V3 (1) It is easy to measure (1) Sediment volume changes

every day by rainfall

(2) Management ponds can be

utilized for other

purposes

110

I/
The data which were obtained by measuring these volumes from 1978 to 1981 are

listed in Table 2.

Table 2

Counted Values by Three Checking Methods

3 "Sediment Volume (m3) Sediment Dry Weight (t)

"Discharge Quantities Discharge Quantities

Sediment Water Settled Sediment Water Settled

Removed Quantities in Pond Removed Quantities in Pond

"(mi) (m ) (m ) (tons) (tons) (tons)

1978 17,227 35,615 29,960 9,027 9,545 9,248

1979 23ý418 39,009 33,278 11,592 11,586 10,574

1980 47,270' 81,073 78,810 26,090 26,757 25,287

1981 38,500. 86,800 77,300 14,660 15,400 14,580

Counted by Counted by Measured Counted by Counted by Measured

soil sur- measuring in pond soil sur- measuring in pond

vey before apparatus vey before apparatus

and after in dredge and after in dredge

Remarks dredging dredging

VI V, V M M M

3 1 2 3

*Ill
BOUNDARY CONDITIONS OF SEDIMENT SURFACES

6- VIEWED FROM DO BEHAVIOR

T. Yoshida

f. Chairman of Technical Committee

Japan Bottom Sediment Management Association

"T. Mimaki

Head of Water Quality Conservation Section

Izumo Construction Work Bureau

Ministry of Construction, Japan

"ABSTRACT

i In measurement of dissolved oxygen (DO) stratifications, the lowest point is chosen usually at a

depth of 0.5 m above the sediment surface. DO

concentrations in the overlying water just above

the sediment are rarely me!asured. Therefore, the

DO behavior in the sediment-water interface is

I not well known. In order to investigate DO

behavior, column tests on DO were performed by

use of special test apparatus. This paper deals

with the.'e test results and discusses the

. - boundary conditions of sediment-water interface

on DO behavior.

"OUTLINE OF TESTS

The test column consists of two parts: the upper and lower sections.

* The latter is the column sampler itself, which has been used for sampling

- undisturbed sediment. Both tubes are connected by a ring coupling in the

laboratory (Figures 1 and 2).

The connected test column is then provided with water jackets at its

circumference and erected in an isothermal tank. In order to emerge from a

thermal stratification in summer lake water, the overlying water column is

heated by three isothermal tanks with different temperatures. Since we had

to measure DO concentrations of very thin layers, we have paid close attention

to water sampling and analysis.

112
6I

AA

row- PW

Sampling 

tubes 

1

U UuCes

-

eeater

"" ~Secdiment

Hete

Figure 1. Test apparatus

The sampling tube (Figure 3) has a diameter of 6 mm, a horizontal length

-of 170 mn, and 8 holes of 0.5 mmo. In the 1980 tests, 4 tubes were inserted

at heights of 1, 10, 40, and 70 cm above sediment, and in che 1981 tests,

- 6 tubes at heights of 1, 4, 7, 10, 40, and 70 cm, respectively. The 15-ml

water samples were taken gently so that the Reynolds' numbers did not exceed

100. Samples were put into the special DO meter, which was designed for this

" test (Figure 4). This meter has a small stirrer for medical use and is capable

of measuring very small quantities of water.

The sediment samples were taken fromi Lake Nakanoumi and one of its inflowing rivers.

THERMAL STRATIFICATION

S Quantities of heat flowing into and out of a segment of the water column

may be expressed as shown in Figure 5.

11:

0II
Figure 2. Photo of apparatus

Sampling

tube

Stirrer

Figure 3. Sampling tube

As equilibrium equation for the heat quanitities is represented as follows:

*3T k D 2T T9 9

3t Gp (1)

where

T =wat er temperature *C

t =time after incubation of tests, days

114
r

( . __1~35 -- "

Figure 4. DO neter

Water Temp.

T z)

"aFlow

k ~pTa --.- 3z.CW raziafe

4%

"Figure 5. Induction of thermal stratification

" w = descending flow velocity due to water temperature difference, cm/sec

Cp = specific heat of water, cal/IC/cm3

k = thermal conductivity, cal/cm/sec/*C

p = water density, g/cm3

z = height of water column

The solution of Equation I is obtained in the following series function:

2

T W 2 7 3W3, z3 (2)

o 4D

"115

4

* , ., - *

* ' , . . 4 " 4 .4.-.
where

T = water temperature at z = 0

P2 0 = water density at 20°C

p p 2 0 (1 - aT) is assumed (3)

2 0 Cp SaP (4)

k(4

2

D thermal diffusivity, cm /sec

Here we calculate

c i 2 0 CP 2.55 x 10-4 x 0.9982 1 x -4 sec

1.42- 1.793 x 102

k= 1.42 °C cm 2

The observed water temperatures are distributed as shown in Figure 6.

These are represented in Figure 7 in terms of the ratio of'oT/T0

cmI00

8t0

t=O t=20

too

~60

10

,J 20

I0 16 18 ZO 22 Z4 26 ZS C

* Water Temp.

Figure 6. Water temperature distribution

-. 116

.o**.
.:: cm

100

90

80

"'i. ,., TO

• 60 1981 1980

"" 50

E

:- 40 0

30

20

10

1.0 LI 12 1.3

ST/To

Figure 7. Ratio of T/T0

Putting the test results T/TC - 1.092 at z = 40 cm (1981) into Equation 2, we can calculate the values of w:

1.9w 2 40 2 7, 3 w3 7_3

1.0912 1+D2 4 24 (1.793 x 10-4) x w x 2i.7 x 403

D 2 24 i0- 

0.092 = 400 w- 1.0995 x 10 w

Neglecting the second term in the right side, we get

"-" 2

2w 0.092 -4

. 2 400 2.3 x 10

= 1.517 x IO 2 -. " D cm-

* Similarly for T/T = 1.1085 at z 30 cm (1980) 0

"w 2

2.195 x cm D

II

II

.I i. 
I€

Takikg D = 1.5 x 1 cm2/sec, we get

w - 1.517 x 10- 2 x 1.5 x 10=3 . 2.276 x 10-5 cmisec (1981)

w = 2.195 10- 2 , 1.5 x 10-3 . 3.287 x 10-5 cm/sec (1980)

"From the water temperature profiles it is found that the descending

velocity (w) due to temperature differences at greater differences is about one

and a half times as large as at lower differences. (This means that the value of w is proportional to temperature difference. The larger temperature difference, thI bigger w.)

VARIANCE OF DO AGAINST TIME

As i1dicated earlier, sediment samples were taken from Lake Nakanoumi and one of itls inflowing rivers. Tap water was used as overlying water.

The relationships between DO concentration profiles and time transfer are

shown in !Figures 8 and 9.

n,

Lake Water DO- 7 '8 mg/L 190

8O

"60

S50

! • 40 • Y o

o

4 30

Zo f ° ~

4 011

in it lotI* too too -

z 4 6 a 10 Mg/t

00

I Figure' 8. 1DO stratification
9

70 @00-0-0

60 Liver Wactr 1981

50

40 o-0-- -

2

30

t-20 t-lo

10[ 00 0

00

Figure 9. DO stratificarion

As the figures show, the initial r)O profile is a nearly vertical line,

located almof4t entirely in the portion overlying the sediment 10 cm above the

interface. DX) concentrations decrease rapidly and approach within 10 cm above

the interface. We can see clearlv that Do concentrations deczeasoe gradually'

according to time and reach a final distribution shifted to the. left in these

f i ,ur s. Their reduction in strong at the lower layers and weak in the upper

layers (Figure 10).

M) STRATIFICATION

From our test results, we have learned that we should con.sider {DO %tratif;cation in two parts. The first part is the distrlbution due to thermal

st i-tiflication occurring in the portion of tile wdter column above the water

laver irmediately nvrrlying the sediment. rihe second part is the distribution

due to sediment oxyyen demand and occurring in the laver immediately overlying

the se(diment.

)19
I

ag/1

14

13

Iz

10 b -70€c

h - 70 ca 90

87

6

b-7 cz

4

3

SZ b 7 cm

I I•

0

• 0 1O s Z days

Figure 10. Change of DO against time

DO DISTRIBUTION DUE TO THERMAL STRATIFICATION

An equilibrium equation of disolved oxygen is represented as follows:

) c I !2c -c-=w-- K-• (5)

where

c = DO concentration, mg/l

w - descending velocity due to thermal stratification, cm/sec

K - diffusion coefficient of dissolved oxygen in the vertical direction,

cm /sec

z - length of water column, cm

t - time, sec

We assume that the solution of Fq(t;ition 5 is a separate function of

temperature (f) at time (t) and z as follows:

120
c - T(t) S(z) (6)

Then putting

Was +Ka2S w-•+ KT'(t) - az z 2

T S(z) n

. - We get

T' -n 2T (7)

a2 S -W +2 (8)

az2 az

From Equation 7

T ce-n t (9)

Equation 8 is rewritten as follows:

a

2

az S 2 W K Tz as + K- 0(0 (10)

(D - D + n - 0

W 2 n

Ký 2 K

n4

-K WW

Thereupon

S(Z) - Cie'lz C2em2z

121
/

Finally

-'e -n2t (Cie lz + C2 e 2 (1)

At the water surface (z = H where H total length of water column), the

following condition is composed of

wC -K - 0 (12)

2 mlH M2H \ 2t mlH m2H)

w e nt (Cee + C 2e 2 Ke-n Clmle + C2 m2 e H 0

'.~~~ (W w( + m a K K )em C1 I + + W +mK)emH2 + m 2 K C 2 = 0

w + rnK mrn H

C2 =W + m2 K e C1

Then we get

2 ~ Fmz w +m 1K (m-n)H + mnz

"CMe C1 e + e ' (13) "w + m..K

This is an equation on DO variance in an unsteady flow.

In a steady flow, the following solution is obtained from the equation:

;,.ac1 a 2 C

w- -K KI. =--

z gz

w c 1 = C1 --Ke (1•)

The curve of Equation 13 or 14 is connected to the curve of the

deoxygenating zone, which is dealt with in the next section. Consequently,

the arbitrary constant C1 is determined by it. Then,

I12

ii 122

!I
IclijC~j(15) "zh z=h

W h sial FY + a)

""'K K K

"' C-- C1w e C0 ssin a

iw

C1 ' eK. sin a

DISTRIBUTION DUE TO THE DEOXYGENATION OF SEDIMENT

The test results showed that the water temperature in the water just above

the sediment (z < 10 cm) is constant (Figure 11). This means that there is no

descending velocity due to thermal stratification. The variance of DO concentrations at this portion is represented as follows:

.4Z

- C.,

0 _

"Figure 11. DO distribution in deoxygenating

zone, cl = DO distribution due to thermal

stratification, c 2 = DO distribution due to

sediment 02 demand

p2

c22 3 = -K C2 c2 (17)

where

" c 2 = DO concentration, mg/Z

2

K = diffusion coefficient of dissolved oxygen, cm /sec

A = deoxygenating rate, sec

123
The solution of Equation 18 is obtained as follows:

c2 e-n t e+ (18)

2 ( ~ 2' - -n ne t s in - -- z +

since C = Co at 0, z 0, we get

A sin a

Equation 18 becomes

2 sin( z +a

C2 CO e sin a (19)

This is an equation of DO variance at the deoxygenating zone in an unsteady flow. In a steady flow, it becomes as follows:

sin z+a

C1 Co sin a(2)

S= 11.5 - 0.2 =3.73 x 10- 5 sec-1 (21).,

11.5 x 3 x 24 x 3600

4 Putting the data together:

"z = 70 cm; C1 = 8.8 mg/. (t = 0)

z = 10 cm; C1 = 7.6 mg/Z (t = 0)

We get

= 0.00244 K

124
"" Since w is already known (page 7), then we obtain

K = 1.345 x 10c 2 / 2 sec

From the observed data,

t 0, C2 11.5 mg/t, and t = 3 days; C2 0.2 mg/.,

we get

0.0527 cm/sec

a, = 0.025 rad

C0 - 1.22 mg/k

Figure 12 shows the DO profile in the deoxygenating zone.

L R

to - __ _ _ - _ _ _

9

4

00

SI Z -3- 4 5 6 7 8 9 10 1I 1Z mgl2

S.-

00

Figure 12. DO profile in deoxygenating zone

BOUNDARY CONDITIONS ON DO AT SEDIMENT SURFACE

As the test results show, we could reemerge DO stratifications in the

laboratory. These behaviors were analyzed theoretically in the preceding

chapter.

125
Li

Owing to the DO stratification, the diffusion of dissolved oxygen travels

from the upper layers to the lower ones, that is, from higher concentrations

to lower ones. The quantities which reach from the top to the sediment surface are -K 2-z per unit area and per unit time. On the other side, some quantities of oxygen are consumed by sediment during deoxygenation, as far as it is

polluted.

These two quantities should be in equilibrium (Figure 13). Then we get

the equation if we represent sediment oxygen demand (SOD) as 02.

~~-. (3l.-,...oxygenat ion

•]•7Figure 13. Equilibrium at sediment surface

0 2 -K 2- =0 (22)

Z=o

A2

S02 -n 2 tK 2 cos z + a)

*0 =K e c 2 o K sin a

-= C° K - cot a e (23)

a

This is a fundamental equation of SOD. From this, we can say that SOD

behaves exponentially against time (Figure 14).

1

126

U
22

Oz Co K(A-n 2 ) cot a - e-n

SOD

Time

Figure 14. Sediment oxygen demand

behavior against time

The total consumption of oxygen (Figure 15) is obtained by a planimeter.

If we represent it mathematically, it becomes

b

Z a

"00

Figure 15. Total consumption of oxygen

e (t o) dz - c(t) dz]

In Table 1, the measured and calculated values of SOD in one sample are

e indicated. The calculated values are obtained from the assumption that

2

"n = 0.11.

"Table 1. Measured and calculated values of SOD

SOD 02/02(0)

2 22

t mg/m /d Measured Calculated

0 400 1.0 1.0

2 320 0.8 0.803

4 250 0.625 0.644

4 6 210 0.525 0.517

8 150 0.375 0.375

127

I
I Z 3 4 5 6 T 1 9 10 days

1.0

0.9

0.8

02/02(0) 0.7

0.6

0.5

0.4

0.3

Figure 16. Comparison of measured and

computed values of SOD

We can see from Figure 16 that there is a good agreement between observed

and calculated values of SOD.

CONCLUSIONS

. The DO stratifications that are often observed in lakes and other water

" areas are well known to pollution investigators. However, there are very few

"* data regarding DO behavior on. the sediment surfacc. From our test result.,, we

can say that the sediment surface is always subject to an anoxic conditi.-

g owing to its oxygen demand.

Frout our tests, we have learned that any DO stratification consists of

"two parts, that is, one due to thermal stratification and one due to the

oxygen demand of the sediment. It was also found that the latter has a small

"height (z < 10 cm).

In winter, no thermal stratification occurs. Consequently, the DO profile

becomes a vertical straight line in most of the water column. In this case, it

•- can incorrectly be considered to extend to the sediment surface.

- The line bends at a large angle at the junction with the deoxygenating

zone (Figure 17).

DO stratification generated in summer reveals an exponential profile

w Kz

4 represented by C1 = C1 K eK

I

128

I
L

- wwo *=o h

in winter in autumn

Figure 17. DO profile

This curve is pulled to lower concentrations (to the left in the figure)

at its lower end by the curve of the deoxygenp.ing zone.

In our tests, we studied SOD behavior from both observation and theoreti- cal considerations. We found that such DO behavior on the boundary layer of

the sediment has a great effect upon the release mechanism of nutrients. How- L0 

ever, this problem was not within the scope of this paper.

(

129

4.~

h"/

i/

m/
FIELD VERIFICATION OF TESTING AND PREDICTIVE METHODOLOGIES FOR

EVALUATING DREDGED MATERIAL DISPOSAL ALTERNATIVES

SDr. R. K. Peddicord

U.S. Army Engineer Waterways

Experiment Station

PO Box 631

Vicksburg, Mississippi 39180

USA

AB STrACT

This paper describes the research approach being

used in the Interagency Field Verification of Testing

and Predictive Methodologies for Evaluating Dredged

Material Disposal Alternatives Program (Field Verification Program - FVP). Evaluative techniques are

being conducted on sediment samples collected from

the channel prior to dredging. The same parameters

will be measured in the field after disposal takes

place. The accuracy of the laboratory predictions

will be determined, and the ecological importance of

the parameters measured will be assessed. This

* information will help shape the implementation of

the environmental reg- 'ations governing dredging

and disposal.

"INTRODUCTION

Environmental regulations in the United States require that proposed

dredged material discharges be evaluated, found acceptable, and a permit

issued before the dredging operation can begin. The U.S. Army Corps of Engineers (Corps) is the regulatory agency which issues these permits after

evaluating the discharge according to guidelines and criteria established by

* the U.S. Environmental Protection Agency (EPA). Section 404 of the Clean

* Water Act (Public Law 92-500) and Section 103 of the Marine Protection,

Research and Sanctuaries Act (Public Law 92-532) require that environmental

evaluations of dredged material discharges include the effects of disposal

on pollutant "concentration through biological processes" (bioaccumulation);

transfer through biological processes" (biomagnification); "effects on fish,

shellfish, wildlife, shores, and beaches;" "transfer through physical

.*i processes" (sediment transport); "species and community population changes;"

and "other locations and methods of disposal including land-based alternatives." At present, some of these evaluations are made using firstgeneration techniques which have not been field verified and therefore

generate data whose interpretation is subject to disagreement. Other of

these evaluations, such as effect on wildlife, shores, and beaches; transfer

through biological processes; species changes; and alternative disposal

methods, are addressed only in a rather cursory and subjective manner

because no objective evaluative procedures have been documented or verified.

130
In order to uphold legal respotsibilities, it is necessary to provide Corps

and EPA field offices with documented and verified procedures for all the

"required evaluations. These must Le accompanied by interpretive guidance

based on documented evidence in order to satisfactorily meet field needs.

The Corps, and to a lesser extent the EPA, have couducted and will continue to conduct the essential first steps of research and development of

theoretically sound and practical evaluative techniques. For those techniques that have been developed, it is essential far their acceptance by other

regulatory and resource agencies to document and verify under field conditions both the accuracy of the techniques and the oveiall environmental

consequences of the predicted changes. The Field Verification Program (FVP)

meets this critical need. The ptogram is a cooperative effort between the

"Corps and EPA and will be completed within a 5-year period. The program is

designed to provide the field with verified procedures and interpretive

guidance for use in assessing the environmental consequences of dredged material disposal under aquatic, wetland, and upland conditions. The Waterways

Experiment Station (WES), Vicksburg, Mississippi, is the Corps laboratory

responsible for the program and will conduct the wetland and upland portions

of the program. EPA's Environmental Research Laboratory at Narragansett,

Rhode Island (EPLN), is the responsible EPA laboratory and will conduct

the majority of work for the aquatic portion of the program.

PROGRAM OVERVIEW

The purpose of the program is to document and verify existing predictive

techniques for use by the field in evaluating the long-term effects of dredged

material disposal. This will be accomplished by achieving three primary

objectives. One is to demonstrate the adaptability of a variety of existing

predictive techniques to dredged material, and to determine the reproducibility of those techniques in the laboratory. The second objective is to

utilize field studies to verify the accuracy of the laboratory predictions.

The third majur objective is to utilize the laboratory and field data to compare disposal in upland, wetland, and aquatic environments in terms of overall impact. To accomplish the program objectives, evaluation techniques

previously developed by both the Corps and EPA will be applied to the routine

maintenance dredging of Black Rock Harbor, Bridgeport, Connecticut. Portions

of the relatively homogeneous dredged material from this project will be

placed in an aquatic dispcsal site, used to create a wetland, and placed in

an upland confined disposal site. This will provide the unusual opportunity

to verify evaluative techniques for predicting impacts in all three types of

disposal environments and allow a direct comparison of the environmental

consequences of the same material under different disposal conditions.

For management purposes, the program has been divided into Aquatic,

Upland, and Wetland areas of investigation. Work units that address specific topics were developed within each rmajor area of investigation. Each

work unit includes both the laboratory documentation of the applicability,

reproducibility, and precision of the technique(s), and the field verification of its accuracy in predicting the environmental consequences.

131

/
/-

The results of the Aquatic, Upland, and Wetland areas of investigation

will be published throughout the program in scientific journal articles and

a comprehensive series of Technical Reports, as listed in Table 1. fhe

information generated in all areas of investigation will be used to develop

a program synthesis report. This report will delineate the usabiliti of

techniques along with interpretive procedures for accurately predicttng

environmentally important consequences from the disposal of dredged material

under aquatic, wetland, and upland conditions.

The FVP was authorized and funded in February 1982. In April, •iih the

cooperation of the New England Division of the Corps, predredging sediments

were collected for physical and chemical charac¢erization and for use in

laboratory predictive testing. A technical agreement between the WEý and

ERLN was developed and signed. This agreement delineates the respon•ibili-

• i ties of the respective laboratories tor the aquatic portion of the p ogram.

ERLN has initiated the aquatic biological studies while the WES has initiated

the upland and wetland plant and animal bioassay laboratory studies., In

addition, the design for the confined disposal site and predictive t~sting

for effluent quality have been completed. Baseline data surveys of the

aquatic disposal site were conducted by ERLN during the summer. The!FVP has

been presented to Federal and state resource agencies and the public.through

public meetings, workshops, and briefings.

The confined disposal site will be constructed during the winte4 of

1982. Disposal operations at the cotrfined disposal and aquatic site4 will

b e conducted during the spring and summer of 1983. Laboratory documentation

of testing procedures for bioaccumulation and consequences of bioaccumulation in aquatic organisms will continue through 1983. Results of th~se

laboratory studies will be reported in 1984 and 1985, through Technical

Reports, Newbletters, and scientific journal articles. Field verification

of the laboratory results at the aquatic disposal site will start ind1983 and

continue into 1985, with results of the field studies reported in 1986.

During dredged material disposal at the confined disposal site, watei quality

will be monito:,d for use In verifying laboratory predictions. Aftet disposal, surface runoff and groundwater will be monitored for determining

potential contaminant movement. Laboratory bioasmay testing wilh upland and

wetland plants and animals will continue through 1983, with field verification studies commencing in 1983 and continuing into 1985. Results oo the

upland and wetland laboratory and field studies will be reported in 0984-86.

CalibratiGn and verification of a three-dimensional (3-D) sediment transport

4 model will be completed and a User Guidance Manual will be available in

1983. A workshop on uses of the sediment transport model will be he~d in

late 1983.

The major effort for 1986, the last year of the program, will be the

technical transfer of the program results. User-oriented products, pjrimarily

in the forms of Technical Reports and Engineering Manuals, will be developed.

These documents will provide the field with documented and vertfied techniques a;,id interpretive guidance for complying with regulatory reouirrim,.nts

for evaluating dredged material. The scientific documentation necE'A:,sry to

* demonstrate the appropriateness of the recommendations will bo establlish<,ý by

* publication of findings in the scientific literature.

"132
The Corps and EPA share responsibility for the regulatory program for

dredged material. Experience has proven that cooperation at the field working level is greatly enhanced when scientists of both agencies jointly

recommend the same evajuative procedures. The FVP should produce similar

increased cooperation at higher levels by uniting the agencies in purpose

and funding at the Laboratory-Division-Region level. This will add to the

credibility of the program among critics and reduce any perceptions of bias.

PROGRAM IMPLEMENTATION-AQUATIC

The Aquatic area of investigation includes four work units. The work

"unit entitled "Bioaccumulation of Contaminants by Aquatic Animals" will

* document the laboratory reproducibility and precision of available bioaccumulation predictive procedures, and verify the accuracy of the predictions

under field conditions. The second work unit, entitled "Consequences of

Bioaccumulation in Aquatic Animals," will evaluate selected physiological

response parameters as indicators of the biological consequences of bioaccumulation and verify these procedures under field conditions. These

p-•,ameLers have been developed by EPA for evaluating effects on fish and shellfish for nondredged materials. Included in these parameters are: scope for

growth (metabolic potential for growth and reproduction), genetic toxicology

(si.Lter chromatid exchange), histopathology (deformities, abnormalities, and

diseases), and changes in adenylate energy charge. Also included in the

work unit is the incorporation of these and other measurewmnts into a hazard assessment protocol for overall impact prediction and assessment. The

third work unit, entitled "Effects of Aquatic Disposal on Community Structure,"

will determine potential impacts of contaminated dredged material on populations and cominunity structure and function in the laboratory and evaluate

the effects of open water disposal on populations and communities in the field.

The fourth work unit, entitled "Dredged Material Movement," involves the

completion of calibration and verification of a 3-D mathematical model for

simulating the dispersion of dredged material from aquatic disposal sites.

Bloaccumulation of Contaminants bv Auatic Animals

Problem

National legislation and international treat,ý require an assessment of

bioaccumu.lation. The reproducibility of test resquts and precision of bioaccumulation predictions made using the current regulatory procedure have

never been determined, nor has the accuracy of the procedure in predi'.ting

actual field conditions been assessed. This information is essential in

order to properly interpret test resultq in a regulatory context and to determine whether alternate or modified procedures evaluated in other work units

ire more useful.

Objertive

The objective of this work unit is to document the laborae'ry reproduci--

bility and precision of available bioaccumulation predic, ,ve procedures, and

to verify the accuracy of the predictions under field conditions.

133

4
Approach

Existing evaluative techniques will be refined as necessary and their

predictive value verified by applying them to this specific dredging project.

Levels of bioaccumulation of selected contaminants over time, the biological

and physical factors affecting bioaccumulation, and the variability in bioaccumulation predictions will be documented in the laboratory. Bioaccumulation

wilJ then be determined under field conditions and compared with laboratory

predictions to verify the accuracy of the prediction methodologies.

Initial characterization of Black Rock Harbor sediments has been

completed. Baseline body uurdens in organisms collected at the aquatic

disposal site were determined prior to disposal operations. Dioaccumulation

of contaminants present in the sediment by a number of indigenous aquatic

. species has been documented in the laboratory. Species examined include the

mussel Mytilus edulis, the polychaete worm Nephtys incisa, and the crustacean

Mysidopsis bahia.

Laboratory documentation of bioaccumulation will be expanded to include

additional exposure conditions and species such as the winter flounder Pseudopleuronectes americanus and the polychaete worm Neanthes arenaceodentata.

Work will be initiated to field verify the bioaccumulation procedures at the

disposal site receiving contaminated dredged material. Chemical analysis of

contaminants associated with suspended sediments will be carried out. Emphasis will be on the comprehensive field verification of bloaccumulation

procedures. Bioaccumulation from suspendtd sediments will be compared with

that frcm consolidated sediments. Chemical analysis of dredged material

after disposal will be carried out.

Consequences of Bioaccumulation in Aquatic Animals

Problem

Dredging operations may result in the accumulation of toxic substances

by aquatic organisms. There is presently no means of assessing the biological

signiflcance of these observed body burdens. This capability is required by

Corps and EPA field personnel to evaluate the impact of dredging operations

on aquatic organisms as mandated by national legislation and international

treaty.

4 Objective

This work unit objective is to evaluate selected physiological response

parameters as indicators of the biological consequences of bioaccumulation

and to verify these procedures under field conditions.

* Approach'

Sev(,ral physiological indices of biological health will be determinec

in orcanisms which h.ave accumulated environmental contaminants from dredged

material. These indices will include: scope for growth, sister chromatid

exchane, adenvlate onergy charge, and histopathological parameters. These

responses will first be determined in the laboratory to establish feasibility

134

! nI III IIi
of use with dredged material and correlation with bioaccumulation. They will

" then be verified in aquatic organisms exposed to contaminated sediments in the - field. In addition, there will be an overview of the consequences of bioaccumulation by integrating the results of all investigations within the program

on the effects of open water disposal. This synthesis will qualitatively

and quantitatively evaluate the methodologies used to assess the consequences

*' of bioaccumulation at the three levels of biological organization (i.e. popu-

" lotion/communities, individual organisms, and biochemical) and to relate

these methodologies with observed levels of tissue contamination.

Baseline data on scope for growth, sister chromatid exchange, adenylate

energy charge, and histopathology were collected prior to disposal operations. . Animal studies include the mussel Mytilus edulis, the polychaete Nephyts

*. incisa, and the amphipod Amplisca abdita. Laboratory documentation of physiological indices of biological stress will be expanded to include the worm

Neanthes arenaceodentata and the crustacean Mysidopsis bahia. The response

of the indices will be documented in animals exposed to suspended as well as

consolidated sediments. Work will be initiated to evaluate the use of these

physiological responses as indicators of biological health following actual

disposal operations in the field. Emphasis will be on field verification of

potentially useful biological responses. Field verification of laboratory

observed physiological indices of health will be conducted. Physiological

Sresponse will be correlated with contaminant body burdens for regulatory

use.

Effects of Aquatic Disposal on Community Structure

Problem

Comprehensive evaluation of aquatic disposal impacts requires that, in

addition to studies using selected key species, communities also be evaluated.

This work unit will evaluate the usefulness of existing procedures for predicting effects on communities, and determine the actual effects occurring

in the field. It is expected that this work will provide a quantitative

basis for addressing the requirements under the Ocean Dumping Act and Clean

* Water Act to assess the effects of disposal on changes in ecosystem diversity,

productivity, stability, and species and community population changes.

Objective

* The objective of this work unit is to determine potential impacts of

contaminated dredged material on populations and community structure and

function in the laboratory and to evaluate the effects of open water disposal

on populations and communities in the field.

Approach

The effects of contaminated dredged material disposal on community structure will be determined by measuring species diversity, biomass distributions,

mortality, reproduction, and the intrinsic rate of growth in selected popula-

"tions within aquatic communities., These population assessments will be

documented in the laboratory and verified by monitoring population and com-

• munity changes in field environments impacted by contaminated dredged material.

135

6
Baseline studies have been carried out to characterize the benthic community and populations in the aquatic disposal area prior to dredging operations. Laboratory studies have been initiated to determine the effects of

contaminated dredged material on the population dynamics of the crustacean

Mysidopsis bahia. Assessment of the effects of aquatic disposal on community structure will begin after dredging operations have been completed.

Species diversity and biomass distribution in space and time will be determined at the aquatic disposal site. Laboratory documentation of the population dynamics of Mysidopsis bahia will czontinue over two years. Initial population densities and cohort frequencies of mysids at the disposal site and

the effects of aquatic disposal on benthic community structure and succession

will be determined. An attempt will be made to correlate changes in population dynamics observed in the laboratory with changes in community structure

observed in the field.

Dredged Material Movement

Problem

Funding to begin the development of a three-dimensional mathematical,

hydrodynamic model was provided by the Corps during 1980-82. Basic model

development has been completed and the model applied to a coastal environ-

* ment. Field data have been collected in conjunction with this effort, but

* model calibration and verification have not been completed. This research

* is needed to provide an accurate, reliable, and economical model to simulate

3-D long-wave phenomena and associated transport of dredged material and

environmental constituents. Comprehensive models for describing dredged material movements in a coastal environment do not presently exist. Such a

model is necessary to assess the potential impact of ocean dredged material

* disposal by delineating the area of possible impact. It will also allow

- -. optimum design-of monitoring efforts by indicating the most appropriate

* . sampling locations.

Obj ective

Completion of calibratinn and verification of a 3-D mathematical model

for simulating the dispersion of dredged material from aquatic disposal sites

is the, objective of this work unit.

Approach

Calibration and verification of the 3-D dredged'material transport model

will be accomplished using previously gathered field data and model runs.

This will provide a documented, user-ready model which will respond to wind

and tide, surface heat and salt flux, river flow, salinity, and temperature

ane surface elevation specified at open inflow boundaries. Based on the

* results of the verification, a decision will be made whether further dredged

material transport modeling work is required.

At present the 3-D model of sediment transport in aquatic disposal sites

has been developed and efforts to calibrate the model usin~g existing field

data have been initiated. kcalib~ration and verification of the sediment

* transport model through reoeated model runs will be continued. The limits

V 136
and applicability of the model will be established and documented in a User

Guidance Manual. A workshop/seminar on the uses of thp model will be

conducted. Simplified techniques for the application of the sediment transport model to regulatory evaluation will be developed.

PROGRAM IMPLEZIENTATION-UPLAND AND WETLAND

The Upland and Wetland areas of investigation include four work units.

The first, entitled "Effects of Upland Disposal on Water Quality," will

document and verify techniques for prediction of water quality effects of

confined dredged material disposal. The sp"ond work unit, entitled "Bioaccumulation of Contaminants in Upland and Wetlaald Plants," will document and

verify plant bioassay procedures to predict movement of contaminants into

upland and wetland plants. The third work unit, entitled "'Bioaccumulation

of Contaminants in Upland'Animals," will document and verify existing

terrestrial animal bioassay procedures to predict bioaccumulation of contaminants in upland animals. The last work unit, entitled "Bioaccumulation of

Contaminants in Wetland Animals," will document and verify existing wetland

animal bioassay procedures to predict bioaccumulation of contaminants in

wetland animals.

Effects of Upland Disposal on Water Quality

Problem

. Section 404 of the Clean Water Act requires evaluation of containment

area effluent water quality. Techniques to. predict effluent quality have

been and are continuing to be developed in laboratory studies. However,

before use of the techniques by regulatory agencies, field verification under

controlled conditions is required. This field study will provide informa-

- tion on the behavior of contaminants entering, moving through, and discharged

"from confined disposal areas as effluent or surface runoff, and will determine potential for leaching of contaminants into groundwater. Integration

of these field results with related research efforts will result in verified

techniques for evaluating water quality effects of confined disposal. These

*i verified procedures will improve impact assessment, reduce constraints imposed

on confined disposal, and allow meaningful comparison of all available disposal options, resulting in monetary and manpower savings.

Objective

. This work unit's objective is to document and verify techniques for

prediction of water quality effects of confined dredged material disposal.

Approach

Appropriate laboratory predictive tests will be conducted on contaminated

*' sediments prior to placement in the confined disposal area. Laboratory

predictions will be verified by field sampling during the filling operation

and surface wvater and groundwater sampling following the disposal operation.

137

I
"The confined disposal site has been designed and will be constructed,

*" operated, and managed to ensure adequate sedimentation and optimum fill configuration. Samples from Black Rock Harbor were collected and a variety

of laboratory tests conducted to determine settling rates, consolidation

rates, and drying rates, and to predict water quality of effluent discharged

during the filling operation. In addition, sediment was placed in a soil

bed in a controlled environmental building and the drying process monitored.

*. At different soil moisture contents, a simulated rainfall event was applied

-* to the soil bed and the quality of the surface runoff determined. Monitoring

wells for determining potential contaminant movement into groundwater were

installed at the site, and water samples were analyzed to determine back-

*. ground conditions prior to filling.

Construction of the confinement structure is planned for early FY 83.

* The confined site will be filled using a small cutterhead dredge. Laboratory

predictions of effluent quality will be verified by field sampling at the

confined site during the filling operation. Water quality parameters will

be monitored extensively in the influent, effluent, and at selected stations

within the disposal area. The disposal area will be managed to provide

both upland and wetland substrate. Following disposal, the quality of surface water runoff will be determined by controlled simulation of rainfall

and collection of surface water samples. Soil erosion control by vegetation

will be evaluated. The potential for groundwater contamination will be determined by monitoring wells around and within the disposal area and collection

*. and analysis of groundwater samples taken before and after filling. Surface

water quality will continue to be monitored as the sediment is dewatered

in the upland portion of the confined site.

Bioaccumulation of Contaminants in Upland and Wetland Plants

Problem

"Current legislation under the Clean Water Act, National Environmental

Policy Act (NEPA), and Resource Conservation and Recovery Act (RCRA)

requires evaluations at or beyond the present state of knowledge and consequently has led to great difficulty, confusion, and ostly project delays

'" for Corps Dfstricts and EPA Regions to properly assess the impact of wetland

and upland disposal of contaminated dredged material. An urgent need exists

to document and verify existing test procedures for predicting contaminant

mobility and bioaccumulation of contaminants in plants under wetland and

upland disposal environments.

Objective

The objective of this work unit is to document and verify plant bioassay

procedures to predict movement of contaminants into plants grown on dredged material disposal sites.

Approach

Limited work has been conducted and first-generation test procedures

* have been developed through other research programs to indicate the potential

mobility of contaminants from contaminated dredged material under upland

138
disposal environments. First-pneration test procedures will be verified in

the field. Bulk samples of sedliment from Black Rock Harbor were collected,

subsampled, mixed, subsampled, 'nd redistributed to those research laboratories

conducting tests. Chemical anailyses were performed on the collected sediment

samples. Index plants were grown and observed for phytotoxicity during a

90-day growth period.

Field tests will be established at the confined disposal site at Black

Rock Harbor. Plants grown in the field tests will be harvested and analyzed

for bioaccumulation of contaminants. Field test results will be compared

with laboratory tests results fr verification of plant uptake prediction.

Plants grown during the second year in the field tests at Black Rock Harbor

*" will be harvested and analyzed for any continued bioaccumulation of contaminants. Second year field test results will be compared with the original

- laboratory tests results and the first year field test results for verification purposes.

Bioaccumulation of Contaminants in Upland Animals

Problem

Section 404 of the Clean Water Act requires that environmental evaluations of dredged material discharge include the effects of disposal on

contaminant "concentration through biological processes." Seve::al Corps

Districts have indicated a need to predict the contamination of animals that

establish residence on upland disposal sites containing contaminated dredged

material. Many of these sites ýave become prolific wildlife habitats despite

the highly contaminated dredged material placed within. Districts have

indicated a crucial need to be able to predict bioaccumulation of contaminants

in animals on these sites before releasing the sites to state and local

authorities for their use.

"" Objective

This work unit's objective is to document and verify existing terrestrial

animal bioassay procedures to predict movement of contaminants: into animals

on dredged material disposal sites.

Approach

Existing upland animal (annelid worm) bioassay test procedures developed

by 3r. C. A. Edwards, Rothamsted, England, for the European Economic Community will be applied and verified for use on contamliated dredged material.

Existing techniques for determining bioaccumulation of contaminants in

upland animals were reviewed. Technical experts in this area of research

weip brought to.the WES to discuss the most appropriate test procedures to

be ;)plied to the Black Rock Harbor sediment. Laboratory bioassay tests

were initiated on sediment fromBlack Rock Harbor using the index animal

species Eisenia foetida (earthworm).

139
"Field bioassay tests will be initiated at Black Rock Harbor to verify

laboratorv test results. Annelid worms will be harvested from the upland

disposal area and prepared for chemical analyses. Results of the chemical

analysis of initial field test animals will be interpreted and field tests

will be conducted for the second year. Other animals colonizing the upland

- site will be collected and analyzed for contaminants. These results will

*. be related to previous laboratory test results with the annelid worm. Field

tests with the annelid worm will be conducted for a third year and compared

- with previous field tests results as well as the original laboratory test

results. These results will be used to further verify the laboratory test

results.

* Bioaccumulation of Coi taminants in Wetland Animals

Problem

Section 404 of the Clean Water Act requires that environmental evalua-

"tions of dredged material discharges include the effects of disposal on

transfer of contaminants through biological processes, i.e., bioaccumulation.

There is a substantial lack of knowledge of contaminant bioaccumulation in

wetland animals. This inadequate scientific knowledge has led to confusion

and costly project delays when Corps Districts and EPA Regions need to

•- assess the impact of wetland habitat creation with contaminated dredged material'. An urgent need exists to document and verify existing test procedures

for predicting contaminant mobility, bioaccumulation, and biomagnification

in animals under wetland disposal environments.

Objective

The work unit objective is to docunleLit and verify existing wetland

Sanimal bioassay procedures to predict bioaccumulation of contaminants in wet-

* land animals on dredged material disposal sites.

Approach

Potential wetland animal bioassay test procedures will be applied and

verified for use on contaminated dredged material.

Existing techniques for determining bioaccumulation of contaminants in

wetland animals were reviewed. Technical experts in this area of research

- were brought to the WES to discuss the most appropriate test procedures to

be applied to the Black Rock Harbor Sediment. Laboratory bioassay tests

were initiated in sediment from Black Rock Harbor using index animal

species Neries sp. (sandworm), Arenicola sp. (lugworm), and Littorina (snail)

as suggested by the technical experts. Laboratory bioassay tests will be

completed and field Lioassay tests will be initiated at Black Rock Harbor to

verify laboratory t •z results. Field tests will continue at Black Rock

ri-arbor to determine ioaccumulation of contaminants in wetland animals during the second year. Other wetland animals that colonize the wetland area

wil be collected and analyzed for selected contaminants. Second year field

test results will be compared with the original laboratory test results as

well as the results of the first year field tests. All test results will be

evaluated for the verification of laboratory test procedures.

140

A_..,

• , - f 
PROGRAM SYNTHESIS

"Problem

Section 404 of the Clean Water Act and Section 103 of the Ocean Dumping Act require that environmental evaluations of dredged material discharges include the effects of disposal on "pollutant concentration through biologi- cal processes," "transfer through biological processes," "effects on fish, shellfish, wildlife, shores, and beaches," "transfer through physical process," "species and community population changes," and "other locations and methods of disposal including land-based alternatives." In order to uphold legal

responsibilities, Corps and EPA field elements require documented and verified procedures for all the required evaluations to accomplish this goal. The results of the FVP will be synthesized into a report that can be used

by the field in selecting suitable predictive techniques and interpreting

the results.

Objective

The program synthesis objective is to document in a synthesis report the ," usability of techniques along with interpretive guidance for accurately pre- dicting environmentally important consequences from the disposal of dredged material under aquatic, wetland, and upland conditions.

Approach

The results of the Aquatic, Upland, and Wetland Studies will be used

to develop a program synthesis report that delineates those techniques along

with interpretive -. 7. dance that can be used in assessing the environmental

consequences ot aquatic, wetland, and upland disposal. Program synthesis will be prepared as a T'echnical Report. In addition, program results will be transmitted to the public through the preparation and submission of

papers to appropriate scientific and technical journals.

PROGRAM APPLICATION

Federal legislation requires the Corps to assess the environmental

consequences of dredged material disposal. The availability of documented and verified predictive procedures will provide the quantitative basis needed for compliance with statutory requirements. Impact assessments of disposal alternatives will be improved with verified procedures, resulting in better decision-making and reduced potential for litigation on environmental issues. Another benefit from the program is, with the ability to quantitatively define the environmental consequences of dredged material

disposal, unrealistic constraints presently imposed on dredging and dredged material disposal can be eliminated, resulting in monetary and manpower savings. Program results will also provide some of the tools needed for

cost-effective dredged material disposal management strategy. Finally, through this program, the Corps can continue to influence the direction of criteria and regulations development and to resolve conflicts with other

regulatory and resource agencies.

141

* *. *. | . .
Results of the program will' provide Corps and EPA field offices with documented and verified state-of-the-art techniques and interpretative guid- ance for complying with the regulatory requirements for dredged material evaluations. Since the work will be conducted jointly by the Corps and EPA, the credibility of the research will be enhanced. The results will be

applicable nationwide, and will become available throughout the 5-year

program.

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STUDIES ON ANALYTICAL METHOD OF ACRYLAMIDE MONOMER

AND ACCUMULATION INTO FISH

"Motoo Fujiki, Junko Asada, and Takako Shimizu

Environmental Medicine, Institute of Community Medicine,

"University of Tsukuba

ABSTRACT

"Acrylamide polymer- is widely used as a coagulant for

the treatment of irdustrial wastewater, domeitic sewage,

sludge, and reclamation and dredging effluent. The poly--

mer includes 0.01% of acrylamide monomer, a well known

neurotoxin.

Data concerning the biodegradability and bloaccumulation of acrylamide monomer are scarce, and an analytical

method' for measuring acrylamide monomer accumulated in

fish has not previously been avaijable. The study reported

herein investigated the behavior of acrylamide monomer in

the onvironment and a method for analysis of acrylamide t•n

fish is described.

Acryla.i.de monomer in fish was analyzed as foýleows.

The fish was homogenized, and the pK of the homoSente was

adjusted to 1. Potassium bromide and potassium brov.ate

were added to the homogenate, and the homogenate was

stored in the refrigerator (5C) for 30 minutes. After

bromination, the remaining bromine was removed by the

"addition of sodium thiosulfate; the homogenate was then

centrifuged. Dihromopropionamide (DBPA) in the supernatant

was extracted with ethyl acetate and measured by GC-ECD.

* The concentration of acrylamide monomer in fish was calcttlated from the concentration of DBPA.

Acrylamide monomer accumulation in carp from 10 ppm

in solution increased rapidly until the 10th day, slowed

from the 10th until the 30th, and then increased rapidly

4, again from the 30th day until it reached 7.65 ppm on the

40th day of exposure.

No accumulation of acrylamide monomer in carp from a

20 ppm acrylamide polymer solution was detected during the

expe-rimental period. Acrvlamide monomer in polymer used

for coagulant did not accumulate in the fish.

147

I..
I

INTRODUCTION

Recent advances in scientific techniques have resulted in the production

of a large number of chemicals useful for improving the quality of human life.

However, some of these chemicals have contaminated the environment during

manufacture, use, and disposal. These environmental pollutants can cause

serious health problems for man. Therefore, it is very important to understand the movement of chemicals in the environment.

In Japan, the Chemical Substances Control Law was established in 1973 and

chemicals are regulated as follows. New chemicals having PCB-like properties

are controlled in manufacture, use, disposal, etc., as a Special Chemical Substance. On the other hand, those defined as Existing Chemicals are examined

for biodegradability, bioaccumulation, and several toxicities.

The Environmental Agency has conducted environmental surveys on chemicals

in samples of riverwater, seawater, rainwater, bottom sediments, and fish.

About 20,000 chemicals are on the list of Existing Chemical Substances and

about 1,000 of these are produced in amounts of more than 1,000 tons per year.

It is impossible to examine all Existing Chemicals for biodegradability,

bioaccumulability, and toxicity. Therefore, chemicals having properties such

as persis'ance, ready bioaccumulability, and strong toxicity are selected from

screening tests as substances to be surveyed in the environment. Many prob-

* lems remain. It is often the case that only some of the chemicals in environmental samples can be analyzed quantitatively.

Acrylamide polymer is widely used as a coagulant for treatmeut of industrial wastewater, domestic sewage, sludge, and reclamatioa and dredging effluent. The toxicity of acrvlamide polymer is slight, but the acrylamide monomer

* contained in the polymer is neurotoxic and readily water soluble. Any use of

the dcrylamide monomer in the coagulant invites serious health problems for

man. Therefore, it is important to understand the etfect of acrylamide monomer on the environment. Figure 1 shows the structure of the monomer and the

polymer.

The toxicity of acrylamide monomer is well known (i-15). However, few

reports exist on the biodegradability and the bloaccumulation of acrylamide

monomer, and an analytical method for acrylamide monomer in fish tissue has

nct previously been reported. In order to clarify the behavior of acrylamide

monomer in the environment, the biodegradability, bioaccumulatlon, and an

analytical method for acrylamide monomer in fish were investigated.

0 (-CH2-CH-)N

CH2=CH-C-NH2 CONH 2

acrylamide (monomer) polyacry(amide

(Polymer)

Figure '. Structure of acrylamide monomer and polymer

148
ANALYTICAL METHOD FOR ACRV!AMIDE MONOMER IN FISH TISSUE

Several reports discuss the analysis of acrylamide monomer in water.

Methods using gas chromatography with flame thermionic detection (16) are not

sufficiently sensitive for quantitation of acrylamide monomer at the partsper-billion level in water. Croll and Simkins (17), Arimitsu (18), and

Nakamura (19) reported new analytical methods for acrylamide monomer in water;

these are discussed below. The monomer in water was brominated, extracted

with organic solvent, and measured by gas chromatograph with electron capture

detector. The sensitivity of these methods is sufficient for analysis of

water contamination at the parts-per-billion level by acrylamide monomer.

However, these methods could not be applied to measurement of acrylamide monomer in fish. In order to investigate the accumulation of acrylamide monomer

in fish, an analytical method was developed.

Exerimental Method

Packing of the Gas Chromatograph Columns

The suitability of several column packings was evaluated by using an

ethyl acetate solution of 2,3-dibromopropionamide (DBPA), which was synthesized from acrylamide by bromination (Figure 2). Cclumn packing materials

including Porapak-Q (50-80 mesh), Unipack-IA (60-80 mesh), Amipack 124 (80-100

mesh), Diethylene glycol succinate (25%, support: chromosorb W, 60-80

mesh) (DEGS), Butane 1,4-diol succinate (15%, support: Chromosorb W, 80-100

mesh) (1,4-BDS), Silicone OV 225 (2%, support: Chromosorb W, 80-100 mesh)

(OV-225), and Silicone OV-275 (2%, support: Chrom-sorb W, 80-100 mesh)

(OV 275) were packed in 1-m-long glass columns and were tested on the gas

chromatograph with electron capture detector (Shimadzu GC-7A). Each test was

carried out with the column and detector temperature, rate of carrier gas

flow, and range and attenuation of detector set at optimum conditions.

Bromination of Acrylamide Monomer

Fifty mirrograms of acrylamide monomer was dissolved in 50 ml of distilled water and tne solution was adjusted to pH 1 by the addition of 6 N

sulfuric acid. Two, 5, 10, 15, or 20 g of potassium bromide was added to the

H H H HH H

I I I ~KBr i I

H-C=C-C-N-H -. H-C-C-C-N-H

II I I II

0. KBr Br Br 0

acryfamide 2, 3--d ibromooropionarnide

(DBPA)

Figure 2. Bromlnation of acrylamide monomer

'49
". solutions and stirred until the potassium bromide dissolved completely; then

S10 ml of 0.1 M potassium bromate was added and the solutions were transferred

immediately to the refrigerator (5°C) where bromination proceeded for

"30 minutes. After bromination, bromine remaining was removed by addition of

1 M sodium thiosulfate solution. The solution was transferred to a separatory

*• funnel containing 50 ml of ethyl acetate and was extracted for 15 minutes.

The concentration of DBPA in the ethyl acetate layer was measured by gas

*" chromatograph. From results of the measurement, the recovery of acrylamide

was determined, and the optimum quantity of potassium bromide was selected.

The optimum volume of potassium bromate and the optimum time required for

complete bromination can also be determined by following the experiment described previously.

Extraction Method From Fish

Extraction method a. One milligram of acrylamide monomer was added into

10 grams of fish homogenate, and the volume of the homogenate was adjusted to

50 ml by addition of distilled water. The pH of the homogenate was adjusted

to pH 1 by the addition of 6 N sulfuric acid. Fifteen grams of potassium

bromide was added to the homogenate and the homogenate was stirred until the

potassium bromide dissolved completely; then 10 ml of 0.1 M potassium bromate was added and the homogenate was transferred immediately to the refrigerator

(5 0 C) where it was stored for 30 minutes. After bromination, bromine remaining

in the homogenate was removed by the addition of 1 M sodium thiosulfate

solution. The homogenate was then centrifuged for 2 minutes at 3000 rpm at

5°C, supernatant was transferred to a separatory funnel, 50 ml of ethyl

acetate was added to the supernatant, and the separatory funnel was shaken

for 15 minutes. The ethyl acetate layer was then separated from the water

layer. The concentration of DBPA in the ethyl acetate layer was measured by

gas chromatograph.

Extraction method b. If a peak of DBPA on the gas chromatogram was

"interrupted by other peaks, the following procedure was followed. The superU natant was transferred to a separatory funnel, 50 ml of benzene was added to

•* the supernatant, and the separatory funnel was shaken for 15 minutes. The

benzene layer was then separated from the water layer. The benzene layer was

transferred to another separatory funnel, 50 ml of distilled water was added

to the benzene layer, and the separatory funnel was shaken for 15 minutes.

r'he water layer was then separated from the benzene layer. The water layer

was transferred to another separatory funnel, 50 ml of ethyl acetate was added

to the water layer, and the separatory funnel was shaken for 15 minutes. The

concentration of DBPA in the ethyl acetate layer was measured by gas

chromatotraph.

Resu I ts

Packia, of( ;as Chromatograph

P'raiak-') and Cnipak-_\ were not usable for quantitation of DBPA.

Chromatorarns of other packings are shown in Figure 3. Tn the case of DEGS

and I. ( Fi~ures 3a and 3b), the DBPA peak was sharp, the separation was

2,)od, and the retention time was suitable for quantitative analysis. However,

the deterioration of packing activity was rapid and the deterioration was

acceilerated by usinu ethYl acetate, and a sharp peak could not be obtained

150
TT-71 -

GC con~dition 4 GC condition

det ector E detectcir ECD *column~ glass coluemIm rcolumn glass coturmim

pack dkifl(g EGS packing 1.4-8Ss

columln temnp. 175 -C ---- column temp. 170 *C -...-- detector temp. M detector temp. 210,C

carrier gJ.3 N~ 80 mt/min. -' - carrier gas N, 40 mtlmin.

senitivity 2'XIO -sensitivity 2

1

Xl0

sampte size 201 - ampf e size 2ut

chart speed smminmin. ____ chart spee-d 5mminin.

a. DEGS b. 1,4-BDS

* 4- J

GC~~ codiio

deetr-C C od tic

column

glassiio T~unr coumTE

pckimng Anpc12 glass columnm Ef (Meeco 

* ~colUMM temp. 110 *C p.clungtm.IS c detector temp. 200t em.C8 77 carrier gas N2 ~30 mi/men . I arrier gag t42 30 M ilm in.

Z .- se1tivity, 2~Xl0 sensitivity 2'X1O

sample size 2utit sAmpie size 2uj ____chart speed 5 mm/imm. _____chart speed smmlmi,n

c. Amipack 124 d. OV-225-

Figure 3. Chromnatogram of DBPA, 0.1 pg/mi (Continued)

151
II

--- I

GC condition

detector E~CO " '-'• column glass columnlm

packing Silicon OV-2 22

column temp. 175"C

-deiecior limp. Q- -9C

carrier gas %4 55 mlmin.

"" sensitivity 21XIO

j .. __ Samole size 2 uz

I . chart spe,-J 5mmimin.

e. WV-275

Figure 3. (Concluded)

after repeated injections. In the case of Amipack 124 (Figure 3c), a DBPA

peak as well as other peaks appeared after injection of DBPA ethyl acetate

solution and the separation was inferior. In the case of OV-225 (Figure 3d),

the retention time was too short and the tailing of the peak was marked and

accelerated with repeated injections. In the case of OV-275 (Figure 3e),

the peak of DBPA was sharp, the separation was satisfactory, and the retention

time was suitable for the quantitative analysis. The peak stayed sharp even

after 100 injections.

Bromination of Acrylamide

The relationship between added volume of potassium bromide (KBr) and the

recovery of acrylamide (DBPA) is shown in Figure 4. The recovery increased

* with the increased volume of potassium bromide until 10 grams, then showed a

constant value after 10 grams. From the results, the volume of potassium

bromide was selected as 15 grams. The relationship between added volume of

potassium bromate (KBrO 3 ) solution an( the recovery of acrylamide is shown in

Figure 5. In spite of the increased volume of potassium bromate solution, the

recovery of acrylamide remained almost constant. From the results, the volume

of potassium bromate solution was selected as 10 ml.

The relationship between reaction time of bromination and the recovery

of acrylamide is shown in Figure 6. The recovery increased with reaction time

up to 20 minutes, but remained constant thereafter. Each accuracy of experiment on additional volume of KBr and KBrO3 , of experiment on reaction time

4 was less than 1.5% as coefficient of variation respectively. From the

.. results, the reaction time of bromination was selected as 30 minutes.

152

I

.. • • .+ • . +. . + . - - +- + + , +. , . + , -. , .. . . *• •. .*. . . . . . • . ._ , * . *
'80-

•80 °80

• 60 .60 >

0 040- U

cr Z40

20 - 0 20

0 5 10 15 20 25 0 5 10 15

K 8r (glSOmr) KBrO3 (mt/SOmi)

Figure 4. Relation between added KBr Figur? 5. Relation between added

and recovery of DBPA KBrO and recovery of DBPA

3

100

".,80 * _ ____.

0"Q60 /

So 40; ,'d4

- 20

0 30 60 90 120

Reaction Time (min.)

Figure 6. Relation between reaction

time and recovery of DBPA

153
"Extraction Method for Fish

The chromatogram of the test solution prepared by extraction method a is

shown in Figures 7 and 8. The sharp peak was obtained from the test solution

of the experimental group, but the test solution of the control group did not

show a corresponding peak. The mean rate uf recovery for 20 pg/ml acrylamide

added to the fish homogenate was 82.0% and coefficient of variation was 1.72%

(Table 1). The test solution of the killifish control group, which was prepared by extraction method a, showed a peak at the same retention time as

DBPA (Figure 9). In the case of killifish, the test solution of the control

group prepared by extraction method b did not show a corresponding peak at

the same retention time as DBPA (Figure 10). The mean rate of recovery of

10 Pg/ml acrylamide added to the fish homogenate was 12.06% and coefficient

of variation was 7.56% (Table 2).

I! --

E-I-

- --• pack inrg SiliconOV275-----,-

7G cotumn temp. 175C

S-..-- ~ detector temp. 190C

. K carrier - gas ': N2 - 35mlI/min. •Control -o

S-- V - sensitivity 2X10 -0- . 77 -- ' Ar__ryt amide

s zsam pte size 2Ur Oafrg/mt

"" _ I chart speedfJ 5mm/min.

Figure 7. Chromatogram of DBPA, Figure 8. Chromatogram of

0.05 pg/ml acrylamide in carp. Extraction: ethyl acetate

1

£

L. 1"54

6:
Table 1. Rate of recovery of 20 ug/ml acrylamide

monomer added to homogenate of fish meat

"(Extraction: ethyl acetate)

Rate of recovery (%) 83.4

81.1

83.4

80.2

81.9

Mean 82.0

Standard deviation 1.41

"Coefficient of variation 1.72

Table 2. Rate of recovery of 10 ug/ml acrylamide

monomer added to homogenate of fish meat

(Extraction: benzen-water-ethyl acetate)

SRate of recovery (%) 12.96

12.13

12.95

11.19

11.07

Mean 12.06

Standard deviation 0.91

Coefficient of variation 7.56

ACCUMULAION OF ACRYLAMIDE IN FISH

Experimental Method

Stability Test of Acrylhuide Monomer in Water

It is well known that the acrylamide monomer is unstable, polymerizes

- readily, and is readily biodegradable. To determine whether or not the concentration of acrylamide in water to be used to raise fish will decrease

stability of the acrylamide in water must be tested for 24 hours before start

of the experiment;

I

155

p.L
79

4d

Ns

°7.

4.. "L-7 .. .... I'"

iC ontro

4 jI

i-_i ____ • ° "

Fi 9 C1.

Id

-.- ____ Controi

1 <on'.trot Cotrot - .5Jt

m Figure 9. Chromatogram Figure 10. Chromacogram of

"of acrylamide in sea acrylamide in sea bream.

bream. Extraction: Extraction: benzen-waterethyl acetate ethyl acetate

156

. - -'• ".- i . " . - - -".. . "-'- - - - - - - - - . -"
* Accumulation of Acrylamide Monomer in Carp kCyprinue carpi-)

Forty liters of distilled wator was poured into each of four 40-1 fishrearing tanks (A, B, C, and D). F'orty milligrams of acrylamide monomer was

added to tank A (1 ppm), and 400 mg of acrylamide monci.r was added to tank B

(10 ppm). Tanks C. and. D were used as controls. Forty carp were put into each

tank and held for 20 days (tank A) or 40 days (tanks B, C, and D) without

feeding. Aeration (600 ml/min) was maintained during the experiment. Rearing

* ~water was replaced wvith fresh water containing acrylamide --very day. Water

temperature was maiacained at 20-22*C during the experim. at. Body length and

weight of carp were 6.0-20.8 cm and 3.0-35.'0 g, respectively. Five to ten

fish were removed from tank A at days 1, 5, 10, 15, and ZO; tank B at day 1,

* 10, 20, 30, and'40; and tanks C and D at days 1, 5, 10, 15, 20, 30, and 40.

These fish were homogenized and the concentration of acrylamide in the homoge-

*nate was measured by analy ti4cal method a (described later in this paper).

Accumulation of Acr-1lamide Monomer in-Killifish (Oryzias latipes)

* Ten liters of artificial seawater was poured into each of three 10-i

fish-rearing tanks (E, F, and G). Ten milligrams of acrylamide monomer was

added to tank E (1 ppm), and 100 mg of acrylamide monomer was added to tank F

(10 ppm). Tank G was used as a control. Five hundred killif ish. were put

* into each tank and held for 20 days without feeding. Aeration (600 ml/min)

0 was maintained during the experiment. Rearing water was replaced with fresh

water containing acrylamide every day. Water temperature was maintained at

20-22*C during the experiment. Body length and weight of killifish were 2.3-

3.3 cm and 0.20-0.25 g, respectively. Sixty killifish were removed from each

tank at days 1, 5, 10,'15, and 20. These fish were homogenized and the concentration of acrylamide in the homogenate was measured by analytical method b

(also described later in thi..i paper).

* Accumulation of Acrylamide Monomer Contained in Polymer in Carp

Forty liters of distilled water was poured into each of four 40-1 fishrearing tanks (H, H', I, and V'). Eight hundred milligrams of acrylamide

polymer was added to tanks H and H' (20 ppm); tanks I and V' were used as

controls. Forty carp were put into each tank and held for 60 days without

feeding. Aeration (600 ml/min) was maintained during the experiment.

Rearing water was replaced with fresh water containing acrylamide polymer

every day. Water temperature was maintained at 20-22*C during the experiment. Body length and weight of carp were 6.0-21.0 cm and 5.0-40.0 g,

respectively. Five fish were removed from each tank at days 1, 10, 20, 30,

40, 50, and 60. These fish were homogenized and the concentration of

acrylamide monomer in the homogenate was measured by ana lytical method a.

Accumulation of Acrylamide Monomer Contained in Polymer in Killifish

* Ten liters of artificial seawater was poured into each of two 10-1 tishrearing tanks (J and K). Eight hundred milligrams of acrylamide polymer was

added to tank J (20 ppm); tank K was used as a control. Five hundred killiKfish were put into each tank and held for 60 days without feeding. Aeration

(600 ml/min) was maintained during the experiment. Rearing water was replaced

157
with fresh water containing acrylamide polymer every day. Water temperature

was maintained at 20-22*C during the experiment. Body length and weight of

killifish were 2.0-3.0 cm and 0.20-0.30 g, respectively. ýixty killifish

were removed from each tank at days 1, 10, 20, 30, 40, 50, ýand 60. These fish

were homogenized and the concentration of acrylamide monomer in the homogenate

was measured by analytical method b.

Analytical Method a

Acrylamide monomer in carp was analyzed as follows. 1-2 cm section of

the fish was placed in the cup of a homogenizer, an amount of distilled water

equivalent to the weight of the fish sample was added, and the mixture was

homogenized. The homogenate was weighed and the volume adjusted to 50 ml UJ

the addition of distilled water; pH of the homogenate was adjusted to pH 1 by

the addition of 6 N sulfuric acid. Fifteen grams of potasSium bromide was

added to the homogenate and the homogenate was stirred until the potassium

bromide dissolved completely; then 10 ml of 0.1 M potassium bromate was added

and the homogenate was transferred to the refrigerator (50C) immediately and

held for 30 minutes. After bromination, bromine remaining iin the homogenate

was removed by the addition of 1 M sodium thiosulfate solution. The homogenate was then centrifuged for 2 minutes at 3000 rpm and 5'C, supernatant was

transferred to a separatory funnel, 50 ml of ethyl acetate was added to the

supernatant, and the separatory funnel was shaken for 15 minutes. The ethyl

acetate layer was then separated from the water layer. Thei concentration of

"DBPA in the ethyl acetate layer was measured by gas chromatograph and the concentration of acrylamide monomer in fish was calculated from the concentration

of DBPA.

Analytical Me:hod b

t Acrylamide monomer in killifish was analyzed as follows. Killifish were

placed in a homogenizer cup, an amount of distilled water equivalent to the

weight of the fish was added, and the mixture was homogenized. The homogenate

was weighed and the volume adjusted to 50 ml by the addition of distilled

water; pH of the homogenate was adjusted to pH 1 by the addition of 6 N sulfuric acid. Fifteen grams of potassium bromide was added and the homogenate

was stirred until the potassium bromide dissolved completely; then 10 ml of

0.1 M potassium bromate was added and the homogenate was placed in the refrig-

- erator (5°C) immediately where it was held for 30 minutes. 'After bromination,

the iaining bromine was removed by the addition of 1 M sodium thiosulfate

. solution. The homogenate was then centrifuged for 2 minutes at 3000 rpm and

V5C, supernatant was transferred to a separatory funnel, 50iml of benzene was

added to the supernatant, and the separatory funnel was shaken for 15 minutes.

The benzene layer was then separated from the water layer. ýThe benzene layer

was transferred to another separatory funnel, 50 ml of distilled water was

added to the benzene layer, and the separatory funnel was shaken for 15 minutes. The water layer was then separated from the benzene layer. The water

layer was transferred to another separatory funnel, 50 ml of ethyl acetate was

added to the water layer, and the separatory funnel was shaken for 15 minutes.

* "The ethyl acetate layer was then separated from the water layer. The concentration of DBPA in the ethyl acetate layer was measured by gas chromatograph

and the concentration of acrylamide monomer in fish was calculated from the

• concentration of DBPA.

158

6

4
Gas Chromatography Conditions

A gas chromatograph with electron capture detector (Shimadzu GC-7A) and a

glass column (length: 1 m, diameter: 3 mm) packed with Silicone OV-275 (2%,

support: Chromosorb W. 80-100 mesh) were used. Column and detector temperatures were 175*C and 190*C, respectively. Carrier gas was nitrogen and the

rate was 35 ml/min.

RESULTS

Acrylamide monomer in rearing water was stable for 24 hours. The time

course if accumulation of acrylamide monomer in carp and killifish from water

at various concentrations is shown in Figures 11-16.

*-The accumulation in carp from water containing 1 ppm acrylamide monomer

advanced slowly until day 10 and then increased rapidly until it reached

0.26 ppm on day 20 (Figure 11).

The accumulation in carp 'rom water containing 10 ppm acrylamide monomer

increased rapidly until day 10, slowly increased until day 30, and then

increased rapidly again until it reached 7.65 ppm on day 40 (Figure 12).

* The accumulation in killifish from water containing 1 ppm acrylamide monomer increased slowly until day 10, and then increased rapidly until it reached

0.31 ppm on day 20 (Figure 13).

The accumulation in. killifish from water containing 10 ppm acrylamide

monomer advanced rapidly until day 15 and then slowly after day 15 until

it reached 25.3 ppm on day 20. The accumulation of acrylamide monomer in

• . carp, killifish, and sea bream from water containing 20 pomr acrylamide polymer

was nondetectable during this experimental period (Tables 3-5).

P DISCUSSION

Environmental pollution by DDT, PCB, methyl mercury, etc., causes serious

problems due to strong toxicity of the pollutants and the rapid rate of bioaccumulation. It is important to understand the behavior of chemicals in the

"- environment. In order to clarify the behavior of the acrylamide monomer in

the environment, the bioaccumulation of acrylamide monomer in fish was investigated. At the parts per million level, acrylamide monomer in water or alco-

'hol solution cdn be measured directly using a gas chr-matograph izith flame

thermionic detzqtor (16), buL acrylamide at parts per billion level concentrations cannot be detected. To attain the sensitivity required, an analytical

method using electron capture detection was developed (17-19). However, problems involving selection of column packings and the technique of bromination

had not been resolved and an extraction method for acrylamide in fish did not

exist. Because of this, we began a study of the subject and successfil results

were obtained. The most important problem of gas chromatographic analysis

involved selection of the column packing. Selection of column packing affects

separation, accuracy, and sensitivity. Nakamura (19) investigated five different packings and reported that ethylene glycol succinate (EGS) had fine sensitivityand resolution. However, the deterioration of packing activity of EGS

A• (and DEGS and 1,4-BDS) was rapid and was accelerated by the injection of

159

-. *.
0.20-

SP0.15

-U

C 0.10 (-0

0.05 I

0 5 10 15 20

Time (days)

Figure 11. Accumulation of acrylamide in carp,

1 ppm acrylamide monomer solution

8

4--, Cn6-

C 4 . 0

2

0 10 20 30 40

Ti m.: (days)

Figure' 12. Accurmnilation of acrylamtde IN carp,

10 ppm acrylamtide monomer solut ion

160

4
0.25 -

0

"Z 0.20 £

c 00-10 I a

750.10.

E A

,0.05 .

S0 5 1 0 5Ti me(days

Figure 11. Accumulation of acrylamide in fish,

1 ppm acrylamide monomer solution

2.5 ,- "

2.0 .0 0

z

Scl.5

"75 E 1.0

0O. 5 carp

015 15 20

Ti me "days)

',4r' 1'• '. ,\cciirtil•.lition of ,tervlatritiv in f ish,

10l 1,1;r ,acr','iJmide monorie.r ;ojutioti

- 0
0.25

0.20

-;0.15

. 0.10

0.05

0 5 10 15 20

Time (days)

Figurt. 15. kccumulation of acrylamide in killifish,

I ppm acrylamide Monomer solution

25-

-20-

- 1

0

--- 105

5-

0 5 10 15 20

T i me (days)

Si•r it). \cctnti,i[,tii i .cr .1 ::'i , iii kin iii'

in) Ii~ m act'- l.x;i,, r•t• ,. 'r .-ý,, it
V.

Table 3. Accumulation of acrylamide in carp,

"20 ppm acrylamide polymer solution

Time of accumulation, day 0 10 20 30 40 50 60

- Concentration of acrylamide 0.00 0.00 0.00 0.00 0.00 0.00 0.00

monomer, ,g/g

Table 4. Accumulation of acrylamide in killifish,

20 ppm acrylamide polymer solution

Fime* of accumtilat ion, day 0 10 20 30 LO 50 60

(oncentration of acrvlamidc 0.00 0.00 0.00 0.00 0.00 0.00 0.00

mo 'imer, .. g/g

00bk 3. Ar:',nvi1lat ;Ion of acr'.xIamide in sea bream,

"21) ac:r?'[x!;r'i !t- polvmer solution

i:'3.' , a c'wri',l ' 1'.. . f'., 3 10 15 20 25

,T r . ,, * r. 1ri:' i, h o .J) 0 0.0 . 00 O .Ot) 0.00

i63
4

ethyl acetate. Using OV-275, the DBPA peak was sharp, separation was

satisfactory, and retention time was suitable for quantitative analysis The

OV-275 also had fine sensitivity and superior accuracy. Therefore, OV-275 was

considered applicable to the quantitative analysis of acrylamide in fish.

In the bromination procedure, acrylamide reacts with potassium bromide

and potassium bromate in the presence of hydrochloric acid. According to

Croll and Simkins (17) acrylamide also reacts with bromine under ultia violet

irradiation. The recovery after bromination (about 60%) decreased by

inhibitors in the reaction mixtuxi. Nakamura (19) reported that acrylamide

reacted with potassium bromide and potassium bromate in the presence of sulfuric acid. Recovery by this methtd was improved and inhibition by anions was

reduced.

fn this study, procedures for b-omination of acrylamide were investigated. In the case of bromination of acrylamide in fish samples, acrylamide

must be isolated from organic substances. We obtained successful results by

tile following procedure. First, the fish homogenate was adjusted to pH 1 by

the addition of sulfuric acid; potassium bromide and potassium bromate were

added to the homovenate before centrifugation; after bromination, the homagenate was centrifuced and the DBPA was extracted with organic solvent. The

recover.' of acrylamide from fish by this method was the same as the recovery

from water.

Ihti rate of accumulat> a of acrylamide ,-onomer in fish was far slower

than the accuHmuJi,at ( f methyl mercury or PCB, in spite of the use of a high

conce-ntration of acrylamide sich as 1 or 10 ppm in rearing water. In the

I ppm solution, the accumulation of acrylamide monomer advanced slowly until

da 1i0 and then increased rapidlv. It appears that the intake of acrylamide

monomer is suppressed in the early days by some action, and then the suppression subsides aad tihe intake increases. In the 10 ppm solution, the accumulation of acrvlamide monomer advanced rapidly until day 10 and then slowly from

day 1i until day 30. TIhe coocentration increased rapidly again from day 30.

Vhe suppression in the early days does not show up and the intake of ".crylamidt, monomer increases rapidly, and the more the intake increases, the more

the excretion increases, so that the accumulation remains constant

,he accumulation of acrylamide monomer in fish from the polymer zas nondetectable. 1he concentration of acrylamide monomer in polymer is approximately 0.01 and usually 1-10 ppm of polymer is used as a coagulant; therefore,

Litb,' pov.'ier-a',c iate.d concLentration of acrylamide monomer is approximately

I. -1 pon. It may beo that at such low concentrations acrylamide monomer is

* itb'Ii t ,is -d rapidly' bv% fi.shi that accumulation does not occur.

CONCLUSTONS

\:n .1ii.t i cal 't:,,t ihod For determinat-,on of acrvlamide monomer in fish was

,t ',it,.. .;' rat- o, accumulation of acr.'lamide monomer in fish * slow

.rc, . .ut •J..• t ieJs the concentration in the rearinp, water (10 ppm) at

. ,acc,:'iuldtion ; acr?'lamide monomer in fish from polymer was

•,,aoL ., ,rere , it is concluded that the uise of acrvlamido polvmer

aj .i , ili.nt r'a' not cauitse Seriotus problems for huillan health.

I i 
REFERENCES

(1) Peter, S. S., aid Herbert, H. S.: A review of acrylamide neurotoxicity,

Part I. Iroperties, uses and human exposure. Canad. J. Neurol. Sci.,

1:143-150 (1974

(2) Peter, S. S., a d Herbert, H. S.: A review of acrylamide neurotoxicity,

Part II. Experimental animal neurotoxicity and pathologic mechanisms.

Canad. J. Neurol. Sci., 1:152-169 (1974).

(3) Pamela, M. F.: Electrophysiological and histological observation on

peripheral nerv? in acrylamide poisoning in man. J. Neurol. Neurosurg.

Pschiat., 32:18H-192 (1969).

"(4) Herbert, H. S., Henryk, M. W., and Peter, S. S.: Ultrastructural studies

on th_ dying-bat k process, I. Peripheral nerve terminal and axon degeneration in systemic acrylamide intoxication. J. Neuropathol. Exp.

Neurol., 33:260T284 (1974).

(5) Richard, J. L., and William, E. R.: Physiologic and pathologic changes

in acrylamide n4uropathy. Arch. Environ. Health., 18:22-2.9 (1969).

(6) Prineas, .'1. Tre pathogenesis of dying-back polyneuropathies, II. An

ultrastructural study of experimental acrylamide intoxication in the cat.

J. Neuropath, Exp. Neural., 28:598-621 (1969).

(7) Pamela, M. F., and Baners, ,J. M.: Periphe:'.ineuropathv in rats produced

by acrylamide. Br. J. Ind. Med., 21 '- -[ (1966).

(8) lilson, 11. A., 4nd Cabe, P. A.: fhe eff,-cis f acrylamide given acutely

or in repeated coses on fore- and hindlin : ..... tion of rats. Toxicol. Appl. Pharmacol4, 47:253-260 (1979).

(9) lennekens, F. (I 1., Veldman, H., Schotman, P., and Cispen, W.: Sequence

of motor nerve terminal involvement in acrylamide neuropathy. Acta.

NCUropathol., 4 :57-6ý (1979).

(10) Hopkins, A. P., and ;itliatt, R. W.: Motor and sensory nerve conduction

velocity in the baboon:normal values and changes during acrylamide neuropath7.'. .. Neurul. Neurosurg. Psychiat., 34:'415-426 (1971).

(11) Hopkins, \A. P'., and Lamhert, E. H. : Conduction in unrnvelinated fibers in

#:.:-p.ri?-lntal itLuroIpathy.. . N' urol. Neirosurg. Psychiat., 35:163-169

S1'-7 .).

,12 A.I;),rt. 1). K.: "Iffects of acr.lamide on thit central nervous system of

i.[ ' cat. I. !' ~r::•acol. Fp. i herap. , 123:180-192 (1958).

S -:i,,.ird, 1). H , Tvs', , . He bert, E. I.., and rhomas, M. A.: The

, i : ,, t,:..ic ',,'ri;'ileral neuiropathies: in vitro efcf.cts of acrvla-

_.i d 2, -ue.',.J:o,.i in brain enolase and other :1\ colvt ic enzymes

;rui: 1 - e .r J, .j 1-: I •I-I.,2 (al'•I).
6

(14) Asbury, A. K., Cox, S. C., and Kanada, D.: 3H-leucine incorporation in

acrylamide neuropathy in the mouse. Neurology, 23:406 (1973).

(15) Peter, S., Lucy, G., Frans, G. I. J., and Willem, H. G.: Polyneuropathies and CNS protein metabolism, III. Changes in protein synthesis

rate induced by acrylamide intoxication. J. Neuropathol. Exp. Neurol.,

37:820-837 (1978).

(16) Croll, B. T.: The determination of acrylamide in polyelectrolytes by

extraction and gaschromatographic analysis. Analyst, 96:67-77 (1971),.

(17) Croll, B. T., and Simkins, G. M.: The determination of acrylamide in

water by using electron capture gaschromatography. Analyst, 97:281-288

(1972).

(18) Arimitsu, H.: Estimation method of microacrylamide in water. Journal of

Japan Water Works Association, 473:10-17 (1974).

(19) Nakamura, H.: The determination of trace acrylamide in water and sludge.

Journal of Japan Water Works Association, 514:37-40 (1977).

1

I

I

" ~166

I-
"SPECIFICATIONS OF A MODEL OCEAN DISPOSAL SITE

FOR DREDGED MATERIAL

W. E. Pequegnat

TerEco Corporation

P. 0. Box 2848

College Station, Texas 77841

U.S.A.

ABSTRACT

When dredged material is disposed at a designated

ocean site, it is planned that the bulk of it will

remain within the site boundaries for substantial

periods of time. But, as is well known,waves and currents of various types are capable of transporting the

material for considerable distances, possibly back

into the estuary from which it was dredged, unless the

site has certain oceanographic specifications. The

concept of an ideal site deals with the issue of what

size and placement of a site will reduce the possibility of mass transport of sediment without unreasonable

increase of disposal costs.

INTRODUCTION

* NATURE OF THE PRESENT STUDY

Although in the United States, and elsewhere, the 1970s saw the growth of

serious movements to ban the disposal of all wastes into the ocean, I sense

that a sentiment is growing today among knowledgeable people that the ocean can

be the most appropriate of receiving environments for salt-laden dredged material. in fact, I accept the proposition that even polluted dredged material

can be disposed safely into the ocean with minor environmental risk, provided

some special care method of disposal, such as clean material capping, is used.

Equally important in mitigating environmental impacts is the application of

special care in selecting and locating the ocean disposal site. This was not

always done in the past, but it is this aspect of the dredged material disposal

problem that I wish to discuss here. My principal focus will be upon the

oceanographic parameters that must be considered if one hopes to define and

situate an ideal or model ocean disposal site for dredged material. Naturally

these oceanographic parameters will change from place to place but mainly they

will differ only in degree.

Although it is very important to understand what oceanographic parameters

must be considered in creating and placing a model disposal site, it is equally

important to apply these factE in an orderly way during the process of choosing

167
the specific location of such a site. Accordingly, as a second major theme, I

shall describe a technique for site selection, referred to as the "sieve technique," that I have employed with some success. But prior to expanding upon

these tLo themes of the paper, it will be useful to review the status of existing ocean dredged material disposal sites in U.S. waters. Some of these may

fit the template of a model site, whereas others will not.

U.S. POLICY ON OCEAN DISPOSAL

Effective management of any activity or resource must be u.'•rgirded by - lucid policy. Thei United States does have a policy governin- ocean disposal.

. It is stated in Sec. 2(b) of the Marine Protection, Research and Sanctuaries

"- Act of 1972, as amended:

*i "The Congress declares that it is the policy of the

United States to regulate the dumping of all types of

materials into ocean waters and to prevent or strictly

limit the dumping into ocean waters of any materials

which would adversely affect human health, welfare, or

amenities, or the marine environment, ecological

systems, or economic potentialities."

Effective regulation of the disposal of dredged material continues to . depend upon the following legal, tools provided to the managers of these

affairs.

-LEGISLATIVE BASIS

Federal legislation controlling waste disposal in the U.S. marine environment appears to have started with the Rivers and Harbors Act of 1899. The

impetus for passage of the Act was public dissatisfaction in the 1870s with the

* heavy pollution of the Hudson River, New York Harbor, and the New York Bight.

*• For a long time pursuant to that enactment, control of disposal of dredged

I material was vested in the U.S. Army Corps of Engineers and the principal criteria for issuance of disposal permits were concerned with whether or not

hazards to navigation or other impediments to transportation would be created.

It was not until the decade of the 1970s that truly effective legal tools with

which to protect the environment of waterways was provided by Congress.

In 1970, again stimulated by concerns of scientists over the impacts of

* disposal of sewage sludge and acid wastes in the New York Bight, the Council on

Environmental Quality issued a report on ocean disposal that stressed the proposition that regulation should be based to a large extent upon environmental

matters.

This report carried recommendations that were incorporated into the Marine

Protection, Research and Sanctuaries Act of 1972 (MPRSA) that regulates the

disposal of wastes into ocean waters.

Sec. 102 of MPRSA authorizes the Environmental Protection Agency to issue

permits for the transportation and dumping of wastes, except dredged and fill

material, and to establish criteria for reviewing and evaluating such permits

and designating sites and times for dumping. Sec. 103 uf the Act authorizes

"168
the Corps of Engineers to issue permits for the transportation of dredged

material for ocean dumping in accordance with criteria established by EPA, as

noted above.

The international aspect of the regulation of ocean dumpin9 was not long

in coming. The International Convention on the Prevention of Marine Pollution

by Dumping of Wastes and Other Matter (The London Dumping Convention or LDC)

was developed in the intergovernmental conference held at London in the fall of

1972. LDC entered into force during August 1975 when the minimum of 15

nations, of which the U.S. was one, had ratified it. I note that Japan became

a Contracting Party in 1981, making a present total of 48 signatory rations.

EPA published the Final Ocean Dumping Regulations and Criteria in the

Federal Register of January 11, 1977, called for in Sec. 102 of MPRSA. They are

"still in force although some modifications are under discussion at the present

time.

"CRITERIA FOR THE SELECTION OF OCEAN DISPOSAL SITES

In the January 11, 1977, document EPA established five general criteria

(228.5) and 11 specific criteria (228.6) to be applied in selection and designation of ocean disposal sites. I shall not itemize them here but. they will be

heeded and mentioned when appropriate as attempts are made to construct and

locate a model ocean disposal site.

SPECIFICATIONS OF EXISTING U.S. OCEAN DISPOSAL SITES

.EOGRAPHIC DISTRIBUTION

There are some 131 dredged material disposal sites officially recognized

by EPA in U.S. ocean wateri. Of these 41 are located on the Atlantic Coast; 4

are in the Caribbean off Puerto Rico; 50 are on the coast of the Gulf of Mexico; 31 are on the Pacific Coast; and the rest are in Hawaii, Guam, and American

SSamoa. The Gulf (.oast accounts for about 70% of the total volume of material

generated by maintenance dredging in the U.S. and the New Orleans District

alone produces nearly half of that.

SIZE DISTRIBUTION

About half of the present dredged material sites are small (0.5 or less

square nautical miles) and an additional 44% are less than 4 square •autical

miles (n mi ) in extent. Only 11 sites (8%) are 4 or more n mi Our

model site will have an area of 3 n mi , but will be compartmentalized into

smaller functional units, as will be discussed later.

DEPTH DISTRIBUTION

Depth is a very important criterion to be applied in placing a dredged

material site. Ordinarily, but not always, depth varies directly with distance

from shore. About 70% of the existing sites have center depths of 20 m or

less. Another 16% have depths between 21 and 99 m, and the remainder (14%) are

100 m or over in depth of which half are in the Pacific where the continental

shelf is narrow. Over half of the shallow ones are in the Gulf of Mexico where

169

* . • • • .. -.
4

the continental shelf is generally very wide. A model ocean disposal site must

be sufficiently deep as to preclude the resuspension of fine-grained dredged

material by normal winter storm waves. As noted later, an ideal site in the

open ocean should be located in water not less than 22 and preferably 25 to 30

meters deep.

/. DISTANCE FROM SHORE

Distance from shore is certainly an important criterion to be employed in

siting both for economic as well as environmental reasons. Economic considerations call for a disposal site to be as near as possible to the chdnnels to be

maintained, whereas environmental considerations generally call for greater

offshore distances to protect beaches and other amenities. Obviously where

channels must be dredged for some distance outward on the shelf, sites may be

near the dredger even though they are a considerable distance offshore. About

half of the existing sites are in the territorial sea, i.e., 3 n miles or less

from shore, while most of the rest are in the contiguous zone 12 or less n

miles from shore. Environmentally, depth and size are more important specifications than distance from shore per se.

OCEANOGRAPHIC CRITERIA FOR SIZE, CONFIGURATION, AND

LOCATION OF AN IDEAL SITE

DETERMINERS OF AN IDEAL SIZE

In the January 11, 1977, revision of EPA's ocean dumping regulations and

criteria we find the following general criterion dealing with dumpsite size, to

wit:

40 CFR 228.5 (d). The sizes of ocean disposal sites will

be limited in order to localize for identification and control any immediate adverse impacts and permit the implementation of effective monitoring and surveillance programs to

prevent adverse long-range impacts. The size, configuration, and location of any disposal site wilTTle determined

as a part of the disposal site evaluation or designation

study. (Underlines added.)

Then in,40 CFR 228.6 (3) we find a specific criterion that relates to size

"a in regard to proposed use of the site, viz., that in selecting a site consideration will be given to:

* I Types and quantities of wastes proposed to be disposed of,

and proposed methods of release, including methods of packing the waste, if any. (Underline added.)

Oi

In selecting the size and configuration of a dredged material disposal

site, it is my contention that one must be concerned with:

a) longshore and tidal current speeds and directions,

b) the proposed average annual amount of dredged material to

be disposed in the site, and

170

6!
4

c) any plans for expansion or deepening of a harbor that would

produce extraordinary amounts of dredged material.

In addition to its configuration, the site should, for management purposes,

be thought of as subdivided into four sections that would be buoyed from time

to time.

SIZE, SHAPE, AND ORIENTATION

The Size of the Site

Study of the volumes of dredged material that Corps of Engineer Districts

n~ed to dispose annually into the ocean reveils i range of from a few thousand

m up to in excess of about 8 million m in the New York District. I

believe that, a site having an area of 3 square nautical miles (10.3 km2 )

E would not only meet the annual needs of all Districts but could accommodate the

material to be dredged for channel deepening. A site of Vhis size is somewhat

larger than the Mud Dump in the New York Bight (7.71 km ) which has been in

more or less constant use for 60 or more years and had until recently some

almost unused portions. Ideally the site would have dimensions of 2.2 x 1.5 n

miles (3.7 x 2.8 km), giving a surface area of about 10.3 million m (Figure

1). Accordingly, shoul 5 the need arise this site could handle in a year as

much as 20-30 million m of dredged material without abnormally high initial

mounding before compaction.

Shape and Subdivisions

For environmental and management purposes the site should take the form of

a parallelogram (Figure 1) with tie smaller sides parallel to the course of the

longshore currents. This will permit disposing of dredged materials along its

long axis without subjecting the same downstream organisms to a constant rain

of fine particulates during disposal. The site should be subdivided (figuratively) into four coylpartments paralleling the ends and each having an area of

about 2.6 million m . In practice muds (silts and clays) should be disposed

in the upcurrent ends of t.e compartments in order to give maximum extension to

the mixing zone.

Location and Orientation

The preferred location and orientation of the site are shown in Figure 1.

In the northern hemisphere the Coriolis effect will cause the low-salinity

current leaving the estuary (harbor) to turn to the right and move down the

coast along with but seaward of the longshore current. At the same time the

tidal bottom water will move in from the left; hence, if the site is located as

shown with reference to the harbor entrance, there will be less likelihood that

dumped materials will be transported back into the estuary, as we shall see

wave forces can accomplish.

"OCEANOGRAPHIC CRITERIA FOR SIZE AND PLACEMENT OF AN IDEAL SITE

DETERMINERS OF AN IDEAL DEPTH

* One of the major concerns in the disposal of dredged material, particularly if it carries some pollutants, is that it should remain in place after

reaching the bottom. T!'2 two natural factors that can resuspend sediments in

171
30.

OFFSHORE CIRCULATION - .

n Mi

LONGSHORE CURRE14T C .R4

00 A - X-:

"4

SUHRFACF CURRENT ES AR

Figure 1. Diagrammatic view showino; the entrance to an estuary with its surface and bottom currents and the pl acement of a dredged material dumpsite in

relation to depth, longshore currents, and offshore circulation.

large amounts are waves and currents, both of which are strongly depth related.

Iisfor this reason that depth is considered to be of paramount importance in

siiga dredged material site.

r WAVES AND THE DEPTH FACTOR F Initial Bottom Disturbance

Certain characteristics of waves must be defined in order to make this

* section understandable:

a) wave height (h) is the vertical distance from the wave trough

to crest. Mean wave heights on U.S. Coasts are ordinarily not

over 0.7 to 1.5 m.

b) wave period (p) is the time required for two successive crests

.to pass a fixed poisnt. Mean wave periods on U.S. Coasts range

between 2 and 5 seconds with maxima ranging up to g or so

seconds.

172

N .o

• o-...1.
. c) wave length (1) is the horizontal distance from crest to crest.

d) wave velocity (v) is the wave length divided by the wave

- .period.

When waves move into shoaling water their peri3ds remain unchanged but

their velocity decreases. Because the period is constant while the velocity

(l/p) decreases, it is evident that the wave length decreases in shoaling

water. Waves begin to feel or disturb the bottom when the ratio between water

depth (d) and wave length (1) d/l is less than 0.5, that is to say when depth

has decreased to one-half the length of oncoming waves. For waves of periods

of 5 seconds this depth is about 20m.

The Threshold of Sediment Movement

As the velocity of fluid flow over the seabed increases, a point is reached where the fluid ,xerts enough shear on the grains to cause them to rise from

the bed and mc'.e horizontally. This point is known as the threshold of sediment movement (Komar, 1976) (1). The shear stress exerted on the bottom by

wave-induced motion stirs up the sediment which may then be moved by a current

that by itself would have been incapable of reaching the threshold stress.

TRANSPORT OF SILTS AND CLAYS

Much of the dredged material derived from maintenance dredging is composed

of silts and clays; hence, we must consider the conditions under which a dispos- * .•ed mound would be subject to transport by waves or currents or a combination of Sboth. Beds of fine-grained sediments having diameters of lO0m or less exhibit a high degree of cohesiveness (Figure 2). Thus, flume studies have shown

that the threshold shear stress for compact fine silt or clay beds can exceed

"that necessary to move gravel-sized material having particle diameters of 2.0

mm or more (Drake, 1976) (3). This cohesiveness is produced by unsatisfied

particle charges,, the strength of which are dependent in part upon water content of the bed, mineral. composition, and content of organic matter. There is,

of course, an inverse relationship between compaction and water content, with a

water content of 80% being of considerable importance (Figurli 2). Drake (1976)

" .(3) has concluded that moderately compact mud beds may be eroded at current

velocities on the order of 10, to 30 cm/sec (0.2 to 0.58 knots) provided the

water content iý no less than 80%. That, however, refers to current speeds 1

m above the bottom; considerably lower velocities are required at the water/ - sediment interface.

"* -. The Shoaling Transformation of Wave Structure

An orbital motion of individual water particles occurs in all surface

0 waves. :n deep water (d/l > 0.5) these particle orbits are nearly circular

with their diameters equaling the wave height at the surface but decreasing

. exponentially toward the bottom. At intermediate bottom depths, the orbits

become elliptical and smaller. When the onrushing waves feel bottom, the

"elliptical motion decays to a back-and-forth motion of the water with the

period of motion equaling that of the surface wave. When this oscillatory

* movement begins it exerts a shear stress on the bottom and the sediment grains

start to fee" the waves 'Figure 3). This stress is several times larger than

the shear e-prted by a steady current of equal magnitude.

173

Ei .? - .. - - i ' . • . " ! > • •• i- i• - . .> -- ' " i - " '' - '¢ " "" ' -. / . /
"K t o o E P 0 5 J 0 4

,0-

S~OEPOSITION

SIUE OIAKI(TI t

Figure 2. Current velocities required to transport sediments having graded

percentages of water. From Postma (1967) (2).

I

140

120

0 2 3,4.;

Figure 3. Expected water depth r'f ;.ediment -.-vem'ent due to surface waves of a

15-spcond period i~nd a range of sediment grain sizes and wave heights. Frbm Korrir and Miller (1975) (4).
There is cornsid.'r-bi' ea idý,rice that at leat in shallow water wave', alone

Cdn produce an orishore s.:di",nt tran¶oort b'-cause of the asy,,rn-try of tneir

corbital mftion. As shuwn in Figure 4, the orbital rvotion under the crest is of

hiah <,;joed but low dir ttiPn, htr-eas the offshore return motion urider the

t rr~uh is of lower spe.-d ',it loriqgcr duration. Sut even .thouh the ,urface

orbital velocities may be auite hiqh, the velocity decreases very rapidly and

hs. os very smnall tin '-ptrs ecess of 20 m. For instance a wave with a 5-

s'<cjnd Perind and a height of I m~i would have an orbital velocity of 100 cm/sec

at the ',jrfare but only I cmr/sec at a depth of 30 m. This bital velocity will

ciuse fine .. nds to t'e t-h/t'.;i2rted t not consolidated MJds.

BN

b -I

-~~ ~ - - -.--- - -

HIcqre 4. tedinent movement under a near-bottom wave orbital motion, the velocity at b unlier the crest is hioher than at e under the trouqh. This causes a

r,,-t onshore movesment of certain grain sizes. From Komar (1976) (1).

Sorrye grain sizes especially of auartz sands may be of sufficient size that

'thoy are transported only by the stronaer onshore orbital motion and are not

-.oved at all by the return offshore flow (Figure 5). A somewhat finer grain

size miqht be moved both during the onshore motion and offshore flow but would

uý)nly shift offshore a small distance during the return orbit since most of the

cujrrent of the return orbit would not be sufficient to move the 'grain. Hence

there would be -a net shoreward movement. Actually in nature the bigger the

particle the more pronounced is the onshore creep (Bagnold, 1940) (5). It is

rf)nceivable that with an offshore current superimposed on wave motion, fine

-sedi'e'nts that are thrown into suspension will be carried offshore while coarser

sediments that remain near the bottom are carried onshore. There are records

indicating that on some coasts sands have been transported onshore from as much

as 20 km offshore (10.8 n miles).

On the other hand when fine material has been resuspended, even. very low

"v-locity currents will tend to carry the material -,horeward and if estuaries or

harbors are nearby much of the material will be funneled into the estuaries and

deposited.

Deposition of silt and some clay will beqin at shelf depths where wave Sjro CIrrents fall b1oqw 5 to 10 cml'ec (sPe Curray, 1960) (6). This depth

, doprni on tho Pxpoyjre of the co.]st hut enenrally ranqPS f-om 20 to 50 m.
o , ttA ¥Ielocity UL4er Waves Sfor Threshol of 5411etmot ion

160

S140

: ,•o, ,-

100

80

~60

20

(."/-.,I, 0l l0, I• Grall 01&" er M

Figure 5. The bottom orbital velocity and wave period (T) necessary for the "Threshold of sediment motion under waves. From Komar and Miller (1975) (4).

Drake (1976) (3) points out that there are two factors characteristic of

fine-grained particulate matter and which tend to greatly increase shelf retention of muds: grain aggregation and interparticle cohesi,,e forces. Shelf

suspended sediments, including those derived from dredged ,naterial, are always highly aggregated. Aggregates with average diameters in tie medium to coarse silt range (31 to 62.5,Am) usually contain hundreds of very fine silt and clay particles bound together by organic matter and van der Waals forces. These

aggregates sink much more rapidly than single clay and fine silt particles. The increased settling rate results in a rapid loss of suspended matter from

surface waters flowing seaward into near-bottom waters that, in many cases,

appear to migrate onshore sl ..y. Often these particles scavenge pollutants from the water column.

LONGSHORE CURRENTS ANP SEDIMENT TRANSPORT

Longshore cur ents play an important role in transporting sediments that

have been broug:,t shoreward by processes mentioned above. If estuaries occur along the coast, some of these sediments will undoubtedly be carried into the

estuary. Longshore currents are generated by breaking waves through two

processes that in some places occur together. The first of these is the long- shore current caused by waves breaking at an angle to the shoreline; the second

is the rip current and its associated longshore currents.
Oblintue Wave Fronts

In most places %aves run up the sloping beach at an angle, but their fall- back is vertical or normal to the beach (Figure 6). As a result, longshore curr-ints are produced which will transport sediments parallel to the coeast.

Some of these will be beach sands but other components may be material dumnped

at sea and carried shoreward. For the most part these longshore currents occur

inside the breaker zone but under certain conditions they occur seaward of this

zone as well.

l4'

Figure 6. Grao)hic portrayal of how a wave train approaching the shore at an angle can create a longshore current.

Rio Currents

Rip currents are always associated with longshore curren-Ls the cause of

which is somewhat more complex than that associated with oblique wave frunts.

When waves arrive at the shore with their crests more or less parallel 'to the

shoreline, there is a small lowering of water level just outside the breaker zone while there is a rise of moan water level inside the surf zone. Since it

will be higher where the breaking waves are largest, water inside the surF zone will longshore flow along currents the 

converge shore to the areas where the waves are smallest. Thus, the toward positions of lowest wave breakers where the

flow turns seaward as rip currents (Figure 7)

• THE SIEVE TECHNIQUE FOR LOCATING AN OCEAN DUMPSITE

DEFINITION

The sieve technique for selecting the location of a dredged material dumpsite involves a methodical, step-by-step elimination of unsuitable areas of the

seafloor, based on economic, aesthetic, acreational, and environmental criteria, until only acceptable areas for its location remain (wee Figure 8we The

unsuitible areas for whiatver reason will be screened out and darkened on the
6L

I ,' NEAO

'.1f~ MASS TRANSPOOT V/~

Ik L ONqG91K) CURRENTS

.. ... .. .......

' . ............. -.----. .

•- " " , . ' . . C ............. . .: ..,'. ... .. ' .

Figure 7. The nearshore cell circulation cnnsisting of (1) feeder longshore

currents, (2) rip currents, and (3) a slow mass transport returning water to

* the surf zone. From Shepard and Inman (1950) (7).

navigation chart. When all such areas have been blocked out, the potential

site areas will stand out in bold relief.

* CONSTRAINTS IN APPLYING THE TECHNIQUE

It is advisable at the outset to arrive at the maximum haul distance from

the harbor entrance that is acceptable for reasons of cost. This distance,

* however, must be large enough Lo intersect the 30-meter isobath. Assuming the

distance to 5e 20 km, an arc of this radius is scribed on a naviqation chart so

that it inte-sects the isobath at each end. At the same time all shipping

fairways should be screened out and darkened (Figure 10). Also, every effort

' should be made to find an acceptable location to the right of the harbor exit, as

noted above.

Assuming a thorough review of the relevant literature and consultations

with appropriate public officials and interested environmental and SCUBA diving

groups have been completed, and mindful of EPA's specific criteria for site

* selection, we shall proceed to scribe on the chart (Figure 9) the locations of

such features as

a) commercial fishing and shellfishing grounds

b) recreational fishing and diving reefs

c) spawning grounds of important species and their food organisms

* d) migration routes of finfish or shellfish inciuding passes into

estuaries

* e) archeological features

f) beaches and other amenities

O
SPONSOR'S ECONOMIC AND

NAVIGATIONAL COMPATIBILITY

0 • PUBLIC'S SOCIO-ECONOMIC

COMPATIBILITY

. -GENERAL OCEANOGRAPHIC

COMPATIBILITY

SITE SUITABILITY

Figure 8. General representation of the sieve technique for siting. Unsuitable areas are eliminated step-by-step until the small white site areas

stand out very clearly.

171)
4

* ®~RECK

CX ARTIFICIAL

WRECKREEF

FISH HAVEN FISH MAVEN

ARTIFICIAL. REEF L A FISH4 HAVEN

WRECK* FISH HAVEN

.SPORT-fiSHING

AREA P (4

AATIFICIA REEF ,SOTFSIGA

S,.-O ISMTFSN AL

~ SPORT-FISHING ARE.A

FISHiNG

AREA

Figure 9. Showing a plot of' senisitive environmental areas of f Mobile Bay,

Alabama, that must be protected by buffer zones and screened out by, the sieve

technique, as shown in Fioure 10.

BUFFER ZONES

Since we can assume that bottom currents may attain speeds up to 0.5 knots

and that much of the dredged material except the very finest would settle out

4 i~n less than four hours, we should protect any amenity and living resource by

establishing the adjacent edge of the dumpsite to be no closer than 2 n mi (3.7

kin) to the amenity, since this is the distance that a 0.5-kt current would

travel in 4 hrs.

Accordinqly, these amenities and their buffer zones are then screened out

by darkening (Figure 10).
LAO4 1AVIGA!IOKAL COMATISIiLI1

II

SCCIO.ECOWNIC CWeATZIILIYY

GENE MA OCI RAJGP IC

COWATIbILITY

To-1il $each Bu.ffer

* haul distance iarcLand th sipig arwys hescon fiur4sow

ares srened ute becaus ofr naueTrsevs andspubtaio bechs

FiTherthirdfigure ashows depth copaibility.hn The fo inal gfiguredshow

all the screened out areas and the placement of the site.
N

0\

The ur, r, cr•.er, -d ar'.,ts that now appear on the chart are suitable for locating the durrpsite. At this point the site will be placed as far down current

from the estuary mouth a, feasible and then much more detailed parameters such

as sediment type can be given consideration in making the final choice.

DEALING WITH EXISTING SITES

Many of the dredged material sites that are in use at the present time in

U.S. waters do not meet the above specifications, because they are small and

located in very shallow water. This does not mean, however, that all of them

I "should be abandoned. Very likely some of these should be eliminated and a more

"" appropriate site established, but others should be maintained even though they

"are less than ideal. It is not appropriate here to discuss this topic in

detail but guidelines for deciding whether a substandard site should be replaced would certainly include

a) Whether the site is located in an open high-energy environment

or in a sheltered part of the coastal environment where normally wave forces are moderate.

b) Whether or not the site receives maintenance dredged material

* from industrial waterways.

c) Whether the site has received maintenance dredged material

during the past five years without observable environmental

"impact and without public protest.

d) Whether or not there are plans to increase the volumes of

material disposed in the site primarily because of new work.

"Many more criteria can be brought to bear on this judgmental matter, but

in my opinion those sites that satisfy even the above simple guidelines might

be given final designation. This would leave time and resources for more careful study of sites that have a history of public concern or that may be scheduled to receive increased volumes of dredged material in the future or that may

be considered for disposal of polluted material, applying "special care" measures. This issue is obviously worthy of further study.

1

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182

0
"L"I TEPATURE CITED

1. Komar, P.D. 1976. The transport of cohesionless sediments on continental

shelves. In: D.J. Stanely and D.J.P. Swift (eds). Marine Sediment

Transport and Environmental Management. John Wiley & Sons, New York, p.

107.

2. Postma, H. 1967. Sediment transport and sedimentation in the estuarine

envirorrr.ent. In: G.H. Lauff (ed). Estuaries. Amer. Assoc. Adv. Sci.,

Wýshirir,ton, D.C.., pp. 158-179.

3. Drake, D.E. 1976. Suspended sediment transport and mud deposition on continental shelves. In: D.J. Stanley and D.J.P. Swift (eds). Marine

Sediment Transport a7id Environmental Management. John Wiley & Sons, New

York, p. 127.

"4. Komar, P.D. and M.C. Miller. 1975. Sediment threshold under oscillatory

waves. Proc., 14th Conf. Coastal Eng., pp. 756-775.

5. Bagnold, R.A. 1940. Beach formation by waves; some model experiments in a

wave tank. J. Inst. Civil Eng., 15:27-52.

6. Curray, J.R. 1960.. Sediments and history of Holocene transgression, continental shelf, northwest Gulf of Mexico. In: F.P. Shepard, F.B.

"Phleqer, and Tj. H. Van Andel (eds). Recent Sediments, Northwest Gulf of

Mexico. Amer. Assoc. Pet. Geol., Tulsa, Oklahoma, p. 221.

7. Shepard, F.P. and D.L. Inman. 1950. Nearshore circulation related to bottom topography and wave refraction. Trans. Am. Geophys. Union, 31(4):

555-565.

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183
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SIMULATION OF ESTUARINE SILT TRANSPORT

ACCORDING TO STORM WATER RUNOFF

Yoji Baba

INTRODUCTION

Artificially polluted wastewater and solids flow into urban rivers

through urbanization and industrial activities. Solids deposit on the estuarine bed due to the reduction of transport ability of the flow.

:" Deposited solids and silt reduce the effective cross-sectional area of

urban rivers which suffer from high runoff rates. At the same time, solids

* both deposited and suspended sometimes contain chemicals undesirable to the

water environment. Their release and suspension damage the river water quality

and the aquatic biota environment.. Precious water-based amenities and natural

property are also damaged.

Fine particles of suspended solids which move in an estuary can form aggregates according to the hydraulic and water quallity conditions such as a

electrochemical Sparticle's properties and surrounding salinity. High salinity

generally produces bigger flocs and aggregates, inlcreases the fall velocity,

and accelerates settling to the bed. The movement! and deposition of the solids

". are characterized by channel scales and salinity intrusion of an estuary.

The deposit of silt behaves as a cohesive material and increases its

density as consolidation proceeds. Flood flows may form a deposit which

contains sand.

"Very soft silt, always alternating between suspension and deposition,

exists near the bank where the flow is slow and is suspended easily by waves

due to navigation and rough weather.

Quantitative analysis of the rate of silt suspension and deposition is

useful for planning dredging projects and water quality reservations in an

• .estuary.

This paper deals with a simulation technique of silt transport when a

storm runoff event is added to the tidal flow motion. The simulation, funda-

"mentally based on a one-dimensional and one-layer model, is successful to some

* degree P-ly by changing the fall velocity longitudinally according to the

"'" magnitude of measured salinity.

- /

• [185 [ REVIOUS PACE

-,P IS BLANK
SIMULATION MODEL

This paper shows a simple simulation model of a one-dimensional and

one-layer system. Of course, a two-layer modelI) or a two-dimensional

model 2) should be used for some salinity circumstances. However, cases where

a simple model like this can be applied will exist.

J The model used herein is described briefly as follows.

Mass conservation for suspended solids takes an integrated form on the

control volume

3ac a C Eac" - B 3E az (1)

5t+T U a~x! A \wo+ 0 ~ Z z

0

where

C: suspended solids concentration averaged in the cross section,

C: suspended solids concentration at elevation z (the bed),

U: cross sectionally averaged flow velocity,

B: channel width,

A: cross-sectional area of the channel,

E: longitudinal dispersion coefficient,

E; : turbulent diffusion coefficient of vertical component,

z

d t: time,

x: longitudinal distance,

z: vertical distance,

4 z : elevation of the bed, and S~0

w : fall velocity of suspended solids.

Mass balance in the vertical will be rewritten as follows:

w + F w C - W (2) 0 zz)z 0 0

Where W = erosion velocity of deposited silt layer and ( Y constant (the

rate of erodible particles to the nonerodible). The fall velocity, wo, depends

on many parameters such as specific weight of a particle, particle sizes, particle concentration, and the scale of flocs and aggregates (this also relates

to the probability of particle contact and to the magnitude of salinity).

186

L7

!/

.- °4
The erosion velocity, W, depends on physicochemical parameters such as

material properties of particles, salinity, duration.of depo~iLion (dei:sity),

critical tractive force, and tractive force of the flow.

:Eny efforts have been conducted to determine quantitatively the magnitude of w and W under different hydraulic and water quality environments.

Here, they are determined by the experimental facts as follows.

Experiments on depositional behaviors of suspended particles •ere carried

out under freshwater conditions in a circular impeller-driven flume (2847.8 cm

long, 30 cm wide, and 29 cm deep).

First, silt is kept suspended in a higher concentration state than the

expected equilibrium through a higher tractive force on the silt bed. The

tractive force is then reduced suddenly and kept constant for about 24 hours

until an equilibrium state of the silt concentration can be reached.

Similar experiments were conducted for both I and 3% saltwater conditions.

The equ'iibrium concentrations reached and the shear velocities (u-) applied

during the experiments have the relationships shown in Figure 1 . The

straight lines drawn in Figure 1 show the tendency depending on the salinity.

Those stra.ight lines are expressed functionally as fi(u*) (i denotes salinity

parameter).

SPP

0- 1000 ,_.-__-_'_

C

1 000,

-0

-- ---- -

0 23 cm/sec

Iz

SFigure 1. R~elationship between SS concen~tration and shear velocity

187

I

t>e
At the equilibrium state, from eqs. (1) and (2,

"" ' B

B (WC w- - aw) =0

A o

So we obtain,

C a (3) w0

On the other hand, from Figure 1,

C = fi(u*) (41)

al•n for equilibrium states. Then we obtain,

-_= fi(u*) (5)

w or 0

As far as unsteady flow computations are concerned, Dronker's implicit

scheme4) is used. For the computation, the discharge is given at 17.2K point

- (17.2 km) and measured tidal level at 0..CK point for boundary conditions.

Time and space intervals for the computation are 60 seconds and 200 to 600 m,

respecti-.ely..

The boundary conditions for SS (suspended solids) concentration calculatidns are given at the upper end and Cs of SS concentration in the, sea at the

lower end (O.OK point) during the rising tide.

A base concentration Co (= constant) 4s also used, which is almost the

same value as the smallest measured, as follows.

Cp = C + Co (6)

where C is the SS concentration calculation and Cp is the final prediction of S~SS concentration.

OUTLINE OF T{E RIVER OBSERVED

Ayase River was chosen for simul-tion and field observations. Ayase

River runs through the low fdnd area located in the southern part of Saitama

prefecture and in the eastern part of Tokyo metropolitan, and finally joins

i,ito Naka River approximately 7 km upstream from the sea. The river has a

2 basin area of 165 km and a total length of 49 km. Water pollution has advanced due to the recent radical increase of population. 4

As water quality preservation measures in the basin, sewage systems are

urged to be provided, and dredging and aeration have been in operation.

Strict standards for wastewater disposal and total contaminant disposal restrictions are hiow in effect. A council has also been irganized for water

quality improvement between responsible authorities and users.

lr

4- ~
Field observations were made in the IS-kin reach (Figure 2) from Kamihirai

Gate (O.OK point) to Matsubara Ohashi (15.0K po'nt). Kamihirai Gate is normally opened freely and seawater usually invades through Naka River. The

point of Natsubara Ohashi is affected by tidal fluctuations.

The lower half of the observed reach is improved and straightened. The

upper half has some bends with relatively great radius of curvature.

Channel width in 25 to 30 m in the lower half and 15 to 22 m in the upper

half. Depth of the flow at the average water level is 2 to 2.5 rn in the lower

reach and 0.6 to 1.6 ra in the upper reach.

The thickness of the deposited silt is shown in Figure 3. Though the

method to determine the thickness varies from year to year, the big

change in the thickness shows the effect of dredging. Generally speaking,

both the reaches above IOK and below 3K seem to have tendencies to deposit silt.

FIELD OBSERVATIONS

Observation points were set up, as shown in Table 1, for water level

observations and sampling.

Twenty-four-hour continuous observations were made both at spring tide

and neap tide. Rainfall and successive runoff occurred during the neap tide

observation.

The time interval of observing i.ater level and sampling water was one

houir. Water level, water sampling (turbidity, SS concentration, and salinity),

suirfAce flow directions, depth of flow, water temperature, and vertical distribution of salinity were observed and recorded. The observations were made

in 4.irch when water temper.iture ranged between 8* and 14*C.

SIMULATION OF SS CONCENTRATION AT SPRING TIDE

Figureq 4,5 , and 6 show the variation with time of water level, saai ty,.

and computed flow d ischarges, respective ly, durir X the spring tide observation.

In the comput.ition proceduire mRntioned above, .a constant fall velocity of

0.1 c'm/Sc(- (eqriiv. lent to the fall velocity of a 3 l-p--,iameter quart," particle)

was tused for simplicity.

As for the ,'rosion velocity, W,

W FXP (0. 719S6ri - 14.,3' . 1) (7)
MATSUUAA QUASha 15.0&

TAKOK 14.5K

TISR110 Sr. 13. OK

TARACTICKTA ITU.5K

4.OI

4'A

190)
46.

0- 10is k

Long. SS Conc.

-- -- 1-

Ob0serve~d S tatio.ns Dis•tance Watpr Level etc. ,

N~amihi rai Gate 0.0 k

Kinegawa Bridge 1.0o

Nakano Bridge 4.0 a

00 U,..

Shin Kahei Bridge 6.5

Ta kumi Bridge 8.3 a

Yanainomiya Bridge 11.8

TeshFro Bridge 13.0 L idn isn

Yakoh 14.5 b

Mat subara "•hashi 15.0 oi

O Indicates observations were conducted.

191
A2 m' 0 01.0SK

I A~~~~ 12.5K _ _ _ _ _ _ _

C- 14.5

1.0

1218 TZ 2 4 6 . 12

Figure 4. Change of water level

O tK

07.OK

A 430K

10,0001 -___: U .~

1,0001,82461

Time

Figure S. Change of salinity with time
3

m3/sec

20,

F

10o

K 8.3K

S-O0 C. 0 13. 0KOK

I Upper

end

-20 _

12 18 24 6 12

Time

Figure 6. Computed discharge

was used to fit to the observed SS concentrations. Furthermore, the values = 0.8, Co = 12 ppm, and Cs = 0 ppm were used. For the boundary conditions,

the discharge at the computing upper end (17.2K) was 0.5 m /sec and measured

SS concentrations at 15.OK were also used.

Computed results, as shown in Figure 7, considerably agreed well with

those measured results.

Computed values both between 2100 and 200 hours and between 1000 and

1200 hours did not agree well. This was caused by the reduction of tidal discharges due to the free outflow from Ayase Gate to Ara River. (The effect

is large when the flow of Ayase River is downwards. This model does not con- sider the outflow and inflow through the gate.)

Though the simulation model is very simple, applicability is not bad.

Functional relationships and zonstants adopted here are almost the same as were used in the simulation of Tama River.

SIMULATION OF SS CONCENTRATION AT NEAP TIDE

Figures 8, 9, and 10 show the variation with time of water level, salinity, and computed flow discharges, respectively, during the neap tide observation.

During this observation, 313 mm of total rainfall was recorded. The runoff

became rem;lrkhle, especially at 400 hours. Computed discharges of the upper

end inclde, both those of the upper end and the tributaries.

1 P3
SS TAKLV)I Br. (8.3K)

SS ~~ATSU "AR O HASHII(1 .5 .0X)

ss -S

0 meaura

24 12 2 6 1 12 I

20-

- ~ IAN jTNGflA r.(1.Of

.2 TIMEure4

0 12 4 612

KNKAUNO Sr. (4.0OK)

0 computed_

PP TIM 24

7 x

PP"

M4

~ 1.0

12 21 24 

Figure 8. Change ofSSwt wtier ltvarl u pont

AP m~

O.OI
10,000..

-. -. -- - -----

~~ ,1

I...... .

1,000~

S.... ... ....

......... 11

___ __ ___ ___ _0 * OK 7\.__L

24 65K

T ime

Figure 9. Change of salinity

191
m 3 /sec

0 8.3K I .

20 .0 13.0 OK

Upper

end•

-IO12 18 24 12

Figure 10. Change of computed discharge,

Figure 9 shows smaller scale changes of salinity than those in the spring

tide. Intrusion of saltwater past Shinkahei Bridge cannot be recognized.

Storm runoff after 400 hours reduces salinity greatly.

Numerical simulations using the same parameters as those in the spring

tide give the results marked by * in Figure 11. By comparing them with those

marked by 0 (measured), good agreement to some extent is obtained, throughout

the reach until the o.- runoff begins. After runoff begins, agreement is

quite poor, especially in the upper reach.

Several improvement techniques can be considered. Figure 11 shows the

tendency to agree well if the fall velocity, w, is reduced longitudinally

after 600 hours. Considering that the variation of w is considerably greater

than that of W along with salinity variations and tha? Figure 9 shows the

longitudinal and continuous variation of salinity after 600 hours (this means

the longitudinal and continuous entrainment of saltwater into runoff water),

it seems rational to give a longitudinal change in the value of the fall

velocity.

Simulation, giving a stepwise variation of the fall velocity as shown in

Figure 12 only after 600 hours, results in the data marked by A in Figure 11.

This small improvement in the simulation resulted in significantly

improved accuracy throughout the computed reach.

196

I
L ;\AA

!iMA73-:ARA ORASHI1(5.OK) TAJtMI Br. (8.3K) AI\

me~asuredI

SS 2 m. easured SS L 0 co~mpuced(constant w

.4 0 cormputed (cons tanc w. ___________________w A 

A uced~varied A cc 

~ 02- E 24 6 IL

A

2 ....~ .2I? SHIN KAkfEI Br.(6.5K) A

A

7-SHIRO Br.(13.OX1_ _ __ _ _ _ __ _ _ _

Ss

1 2 Z4 6 t

?FM .:Mr- SSNAKANO Br. (4,.OX)

~*Q0* 

A~ -,o

YkNAG-,i4CKA -7 r 8 A 12 18 :--4F 24 1 2

0 KHINEAWA Br. (1.0K)

*6

0.2 t87M 4 6 12

Figure H. range of SS0

L 7
cm/sec

0.1 ~i

0.05

Wa

0.01

0 5 10 15 km

DISTANCE

Figure 12. Change of w according to reach distance - 0

CHARACTERISTICS OF SS LOAD PASSING THROUGH THE STATIONS

The numerical simulation model presented here can be used with some

accuracy for predicting SS concentrations in Ayase River at desired points

under several hydraulic conditions with longitudinal movement in suspension

and deposition of SS.

Longitudinal characteristics of movement and deposition of SS along the

reach concerned are estimated by computing 24-hour load integration at the

observed stations both in the spring and neap tide. Figures 13 and 14 show

the integrated SS load for a 24-hour period. Figure 13, At the spring tide,

demonstrates a go-and-return movement of SS load following the tidal motion,

especially at the lower reaches. However, even at these points, net SS load

is transmitted downstream.

The quantity of transport is very small at the upper reaches. The

integrated volume for 24 hours at each station becomes greater the farther 6

downstream one goes. At spring tide, this means SS load is transported downstream and the erodible river reach incurs a small amount of deposition.

On the other hand, at neap tide, including the storm runoff event, the

amount of silt transport is small and a considerable amount of. SS load occurs

when a rainfall of 35 mm is recorded (SS load transport intensity per unit

time is great, especially at upper and middle reaches, and matches the spring

tide).

Integrated volumes for 24 hours show the erosion between Yanaginomiya

Bridge and Takumi Bridge and deposition between Nakano Bridge and Kinegawa

Bridge. The greater amount of deposition downstream of Nakano Bridge includes

the loss due to the outflow from the Ayase River to the Ara River. .

198 .1 ..

So
tons ________

150 1._ OK-

-v 4. O.K 7---- t

C 6. 5K ____ -

S 8.3K __ -

A, 13.0OK

u 15.OK - - - - - --

100-

0 50

77 7ýý -- =7_

z %__ -- _

.0i

j !77.;: 

12t 28: 24 ______ t: 

:7Z.=e

Fi ur 13 T..i.e r ti no.S.o d, s r ng t d

JS

99.. ...

- - 7,- := :-
tons

100 I

/ -:

0 1.0OK

_L R __ 

-- * 7 6.5K

50 0j ~ ---- : A 13.0 OR

U15.0K

1 - .218 2___4 ..:~z y:6>K~-- 12

Time.

Figure 14. Time integration of SS load, neap tide .-

In conclusion, the observed reach of Ayase River is expected to have

erodible channels during spring tide, small amounts of SS transport during

neap tide, and more depositional channels downstream of Nakano Bridge when

storm runoff occurs.

It will be possible to prcdict depositional behaviors (Figure 3) along

the observed reach if several observations are made during storm runoff.

1001
CONCLUSIONS AND RECOMMENDATIONS

The following conclusions and recomm-ndaLions can be drawn from this

study:

a. Suspended solids transport along tsie Ayase River reach is

"numerically simulated using a one-dimensinnal and one-layer

model. The concept of the erosion velocity is used which is

determined qualitatively based on experiments.

b. The simulation is satisfactory under the condition of a constant

w value both at spring and neap tides.

c. In case of a storm :,noff, in which the rutoff rate is not negligible, longitudinal -hanges of the w value with the salinity

level provide a usef-.I tool in obtaining a satisfactory

simulation.

d. HowE-ver, relevant values of w with the runoff sc'le are not

now known. 0

e. Under the hydraulic conditir is th0' cause a definite salt wedge

to form, the simulation .I can )t be applied.

REFEý iCES

1. Odd, N.U.J., and Owen, M.W. 1972. "A Two Layer Model of Mud Transport

in the Thames Estlary," Proceedings of the Institute of Civil Enjin'rs.,

Paper 7517-S.

2. Ariathurai, R., MacArthur, R.C., and Krone!, -. B. 1977. "Mathem.atical

Model of Estuarial So-din,-nt Transport," Technical Report U-77-12, U.S. Army

Engineer Waterways Ex:,er".mert Station, CE, Vicksburg, Miss.

3. Baba, Y. , and Iwa i, K. 199O. "Silt Transp)rt by Flow in an Estuary,"

The 24th Conference on K:ydiaulics, JSCE.

4. Dronkrs, J.J. "Tidal Computations for Rivers, C.agtal Areas, and Seas,"

Jour. ASCE, Vol 95, No. HYI.

20 I
RESCUING THE PORTS

AN UPDATE

H. R. Haar, Jr.

Board of Commissioners of the Port of New Orleans

P. 0. Box 60046, 2 Canal Street

New Orleans, Louisiana 70160

ABSTRACT

The environmental movement in the United States

of the early and mid-seventies began exacting its

toll on the ports of the country in the late seventies.

ThWs toll is in the form of time delays in obtaining dredging and dredged material disposal permits, denial

of permits, delayed capital investment improvements, increased investment and operation and maintenance

costs, and lost revenues. To counter these impacts

and to seek state-of-the-art practices in dredging

and dredged material disposal activities, both the

American Association of Port Authorities and the

InternAtional Association of Ports and Harbors estab-

,lished ad noc dredging committees. Since late 1979

these two organizations separately and jointly have

pursued similar goals to obtain political recognition

and acquire influence to alter United States legislation and international convention. Decisions governing

ports and port operations engaged in international

trade must be made in the overall public interest and

welfare and not excessively hampered by environmental

considerations alone. Achieving organizational goals

will require continued effort, organizatinnal funding, and exploitation of opportunities to tell the story.

INTRODUCTION

Dredging and disposal of dredged material are essential operations in

mainLaining the navigability and economic vitality of ports throughout th,.'

world. In tVe United States, more than three hundrpd and fifty (350) mil- I

lion cubic yards of dredged material per year are dredged from more than 100

port, servirg the nation. More often than not, viable disposal options are
limited, and ocean disposal of this material becomes thelmost economical

alternative, least damaging to the environment, and che 6nly practical method of disposal.

One example of the importance of ocean disposal of credged material to

United States ports and the national economy of the country--and one which I

am most closely associated with--is the situation in the lower Mississippi

River. Here, there has developed a vast deep-draft purt compiex stretching

from Baton Rouge to New Orleans to the Gulf of Mexico--essentially a 234-milelona port complex that, in 1979, handled 364 million tons of waterborne

cargo, foreign and domestic, excluding shallow-draft, through-traffic cargo.

The Port of New Orleans, itself, has become the number one port in the

United States in total waterborne commerce, foreign and domestic, deep- and

shallow-draft, ocean and coastwise commerce tonnage at 177.3 million tons

in 1980. According to the Department of Commerce, the Port of New Orleans

retained its number one position in foreiqn waterborne cormerce with 58.3

million tons in 1981, while Baton Rouge was listed as fifth in the United

States with 30.8 million tons.

Maintaining oceangoinq ve~sel depths at the Mississippi River-Gulf

Outlet and the Southwest Passes of the Mississippi River to the Gulf of

Mexico has necessitated dredging over the pdst three years with an annual

average disposal of 6.24 million cubic yards of dredged mIterial into ocean

waters. Due to location and volume alone, ocean disposal of dredged material

is the only feasible method of keeping this vital shippin• area open.

DISPOSAL OPERATIONS AND ASSESSING THE ENVIRONMIENT

Ocean disposal operations, however, have come under close ervironmental

scrutiny. arany ports throurhout the world. and tiArticularly tho,- in th,.

'jinitnd Statps. ara ,•x:)#,ri~nif,; ircrea-,ep difficulty in oo tainin-; the niecPssar)'

government permits to accomplish the dredging required foo normal operation

ind maintenance activities as well as capital improvenenti. Periodic maintenance drpdqinq is essential for operations at seaports. Delays in perfor-rinq this maintenance often mean lost revenues, increased shippinq costs,

and decreased port efficiency. These imipacts affect Lhe very economic

vitality of a port.

Tho• ports of the United States began feeling the pressures generatcd by

new eomrorrpntal laws during the early and mid 70's. Mandates of the

'National Environtental Policy Act of 1969; the Fpdpral Water Pollution Control I:.ct rf l'719 I the Marino Protection, ResParch. and Sanctuaries Act of

197,"; ari :)th'or feppral laws ivrpacted PY-ansivoly on the jcopo and comolexity

*;, hp fpjor,a roqu•Iatory proqram ovpr , • and channel construrtinn and

,J~j0) irC rlaintnn,•nor artiviti.'s. The Adiministratnr of the Environm~ental

P ,,, "> A'p~r 'j SEPA), in cOnuor; tiorl inith th9" Spcrntarv of the Ar•,y. was

ro;r-or• e,•/o p r•gulations controlling dre'1giTr and fillinq activities

in ,aitr- )f thc, United Statps and adjacent wntlands and controllinq disposal

of 'djred -,aterial in ocoan water. (ocpan dumping). TheSe activities r,'*1Wre

.20 3
evaluation and assessment of probable impacts on the marine environment,

wildlife habitats, and, in general, the overallenvironment of man to

include the impact on the well-being of man, himself.

Chemical analyses of materials to be dredged were required after the

regulations were promulgated in 1974 and 1975. Soon afterward, water column

chemistry was additionally required in the preparation of impact assessments.

The degree of testing accuracy was greatly increased when EPA published its

"Quality Criteria for Water" in July of 1976. Costs and time required to

obtain permit approval were increased considerably.

On January 11, 1977, the United States Environmental Protection Agency

revised the "Ocean Dumping" regulations and criteria, requiring additional

testing of materials to be dredged. An interim test procedure called

"bioassay" was included. Marine organisms such as juvenile shrimps, clams,

worms, and fishes are exposed to sediments and water taken from the site to

be dredged. Organism survival is evaluated after ninety-six hours. After

ten days, the tissues of certain surviving organisms are analyzed for

chemical content which would provide an indication of potential for bioaccumulation. On September 7. 1977, the bioassay test procedure became

mandatory in evaluating ocean disposal of dredged material.

'A Case Stuýq--Port of Lake Charles and Calcasieu River

On November 22, 1977, the U. S. Army Corps of Engineers notified Region

VI, U. S. Environmental Pi 3tection Agency, of the intent to perform maintenance dredgin' of the Gulf approach channel to the Calcasieu River and its

inland reach.

Considerable discussion developed over the need for bloassays because

of exclusions provided for in the regulations. On February 15. 1978, EPA

refused approval of tie permit until receipt of bioassay results. Bioassays

were then run by a contractor, but results indicated a potential for acute

toxicity for marine organisms in direct contact with the sediments. The EPA

again disapproved the disposal operations, and, thus, the dredging, on July

3, 1978.

The "Ocean Dumping" -egulations provide that if the material proposed

for dumping does not meet the criteria, the District Engineer may determine

that no economically feasible alternative method or site is available and so

notifies EPA's Regional Administrator. The District Engineer submitted a

report of these findings to the Chief of Engineers on October 11, 1978, and

reiuested that he certify these facts to the Secretary of the Army and

rRLuest thit the Secretary seek a waiver of the criteria from the Administrator. Additional supportive inforrnution was provided to the Office of

the Thief of Engineers, and the Secretary of t, Army subsequently requested

1hp waivpr fror' the Administrator. EPA, on Febru:,ry 7. 1979. Again, addit•,ad inforliation was requested by EPA (this was the first waiver request

oehich they had received). On April 18, 1979, EPA gr',ritpd a partial waiver to

Mile 10 fur maintenance dredging. Eighteen months elapsed from the timt of

the ori'inal reo,;est to granting of the partial waiver--and iL -as not until

204
January 7, 1981, that the Administrator of the EPA informed the Secretary

of the Army that he granted unconditional approval fo- the disposal of the

maintenance dredging material from the entire requested dredging area into

the ocean. In rendering his determination, he found that such dumping would

not cause undue degradation to the marine environment. In reaching this

decision, a period of over three years had elapsed.

Such delays are costly. But even more staggering is the fact that if

this problem had not been resolved and alternative disposal sites had been

required, the annual maintenance dredging costs would have escalated from

$1.1 million to S62.9 million as measured against an annual project benefit

of only 521.0 million. It would have also involved thousands of acres of new

dredged material disoosal areas.

,ORGANIZING FOR SURVIVAL

The Ainerican Association of Port Authorities

In response to such ever-increasing problems of delays and escalating

costs and to continue efforts of those proposing more stringent, if not

always applicable, testing procedures, The American Association of Port

Authorities (AAPA) established an Ad Hoc Committee on Dredging in June, 1979.

(The Committee is now known as the Special Dredging Committee.) Its establishment was recognition that the then existing AAPA Committee structures and

ensuing resolutions were ineffective in moderating the trend toward increasing

environmental restrictions on dredging activities. Early on, goals were

established. These goals included the identification and documentation of

those laws, rules, regulations, agencies, procedures, and agreements which

are creating dredging problems. Targeted for study were concerns over mitigation, compensation, endangered species, bioassay test criteria, local

costs, permit delays, and interagency agreement. Additionally, the Committee

was charged with developing recommended re-isions to existing regulations and

procedures that would provide needed relief as well as the necessary documentation to support those revisions. Finally, the new Committee was

instructed to develop a strategy to be used to achieve adoption and implementation of these revisions and to compile data on key legislators,

committees, boards, and administrators to whom these revisions must be

officially transmitted.

The International Association of Ports and Harbors

In early 1980, a similar committee to coordinate on the international

scene was established by the International Association of Ports and Harbors

(IAPH).

At the !APH Exccutive Board Meeting in Brisbane, Australia, in April,

1980, there qas considerable discussion of the problems that the United

States ports had been encountering in their attempts in recent years to

dredge their facilities. The Board recognized that those difficulties

stemmed in a large measure from the United States being party to the "Convention on the Prevention of Marine Pollution by the Dumping of Wastes and

205
Other Matter," negotiated in London in November of 1972, and more commonly

called the "London Dumping Convention" (LDC). Further, the Board agreed

that it would be to the benefit of the IAPH membership to develop a better

understanding of port dredging practices and the relationship of those practices to the terms of the London Dumping Convention.

The missions of the International Ad Hoc Dredging Committee dre:

1. To review, report, advise, and submit recommendations on major

matters relating to seaport and inland port dredging and dredging equipment;

2. To meet with and coordinate with the London Dumping Convention and

the Inter-Governmental Maritime Consultative Organization (IMCO), the latter

being the organization Jesignated to serve as the Secretariat to the LDC;

3. To develop a program on disposal of dredged material problem areas

for inland ports;

4. To publish an inventory of dredging equipment owned by dredging

companies worldwide, including a special section on new, innovative equipment;

5. To collect and publish information on the state of the art;

6. To publish an information brochure on sources of information and

assista.ice on dredging techniques and types of equipment best suited for

given situat..ions.

WORKING TOWARD THE GOALS

These two committees, the Ad Hoc Dredging Committee of the IAPH and the

Special Dredging Committee of the AAPA, have pushed forward in their efforts

to resolve regulatory problems confronting the industry and to seek, as well,

solutions that are environmentally and economically sound.

On March 14, 1980, AAPA representatives appeared before the House Committee on Merchant Marine and Fisheries to del'iver a supporting statement on

H. R. 6361, entitled "A Bill to Amend the Marine Protection, Research and

3anctuaries Act of 1972 in Order to Suspend Temporarily the Use of Bioaccumulation and Binmagnification Testings in the Evaluation of Applications

Relating to Ocean Dumping of Dredged Material, and for Other Purposes."

As a result of this hearing, action was taken to

develop proposed amendments to the Marine Protection,

Research, and Sanctuaries Act of 1972. These amendments, which would resolve many dredging problems,

were provided to several U. S. Representatives who

promised to co-sponsor the necessary legislation.

Through a meeting on March 19, 1980, the White House authorities of the

Carter Administration, the Special Dredging Committee, and the AAPA at large

derived substantial benefits and positive direction. The meeting included

m m'
AAPA leadership members and was held to provide an opportunity for discussing

dredging problems. The group, including myself as the AAPA Special Dredging

Task Force Chairman, met with Mr. William G. Simpson, Deputy Assistah~t to the

President; and Mr. David M. Rubenstein, an Assistant to Mr. Stuart E.

Eizenstat, Assistant to the President for Domestic Affairs and Policy. Our

appeal for support in dredging activities was delivered. We were cautioned

that budgets were being cut. Mr. Simpson later advised us that we needed to

make stronger and more frequent representations to Congress and involved

government agencies.

The ;iembers of the AAPA Special UrLdging Committee believed that the

AAPA could provide influence on ocean dumping controls if AAPA became involved in the United States EPA-chaired Committee on Ocean Dumping, a Subcommittee of the U. S. State Departmaent Shipping CoordinaLing Committee. This

Subcomnittee was formed in 1I76 to provide an opportunity for public and

government interagency comments and advice on United States policy relating -*

to the London Ocean Dumping Convention. As Chairman of AAPA's newly organized Dredging Committee, I requested in June, 1979, that the EPA appoint me

as a member of the Committee on Ocean Dumping, also frequently referred to as

the "Advisory Committee on Ocean Dumping." The appointment was finalized on

August 15, 1979.

Fifth Consultative Meetina, 1980

During 1980, it became apparent that the EPA-chaired Committee on Ocean

Dumping was dominated by the outlook of the parent agency (EPA) and sometimes

unfounded concerns of environmental organizations and, thus, would not provide the vehicle to influence ocean dumping criteria so as to enhance

dredging programs clearly in the national 4nterest. A direct appeal to the

London Convention appeared to be the only hope. This was achieved through

the cooperation and assistance of Mr. Anthony J. Tozzoli, Port Authority of

New York and New Jersey, who is a Vice President of the International Association of Ports and Harbors and, at the time, was also Chairman of that

organization's Dredging Committee. Through his good offices, it was possible

to arrange for the AAPA Dredging Committee Chairman, who is also a member of

the IAPH Dredging Committee, to head an IAPH delegation with observer status

at the 1980 Fifth Consultative Meeting of the Contracting Parties to the

London Dumping Convention held in London, September 22-25, 1980. This convention is the major global treaty governing the ocean dumping of wastes,

including dredged materials. It should be noted that as signatory to this

convention, the United States is bound by the adopted international rules and

criteria in promulgating national laws and regulations.

In appearing before the London Convention, the IAPH representative presented a position paper directing the attention of the Contracting Parties to

possible interpretations of the terms of the LDC and their subsequent application to ocean disposal operations of dredged material. Application of

differing interpretation could result in an absolute prohibition of ocean

dumping of dredged material--even when there may be no feasible or practical

alternative means of disposal, and even when the disposal might be safely

carried out if special care is taken. This, it was pointed out, could

207
threaten world ports with closures resulting in devastating economic impacts

upon the flow of international commerce. IAPH urged the Contracting Parties

to consider these possible effects upon port operations. The IAPH also proposed a study on the dredged material issue with a view toward adopting

whatever changes are needed in the LDC to ensure that there will be no un- r

intended or unnecessary interference with essential port operations.

The concerns expressed by the IAPH delegation at the Fifth Consultative

Meeting were well received. The Contracting Parties recognized the signif- .

icance of the technical issues raised by the IAPH, namely, the use of

"special care" in the ocean dumping of dredged material. The consultative

parties directed that these issues be considered by the Ad Hoc Scientific

Group of the Convention at its next intersessional meeting of May, 1981, and

to report to the Convention 3t the Sixth Consultative Mleeting held in London

in October, 1981. The Conti-acting Parties also agreed to consider during the

intersessional period administrative/legal issues raised by IAPH as they -.

relate to the application of the Convention and to address such issues at the

Sixth Consultative Meeting of the LDC.

IAPH employed a technical consultant in the environmental field, Dr.

Willis E. Pequegnat, an oceanographer for Texas A & M University, to-develop

on a priority basis a technical paper for presentation to the international

Ad Hoc Scientific Group. The paper focused upon the "special care" measures

raised by the IAPH delegation during the Fifth Consultative Meeting. Dr.

Pequegnat advanced the basic premise that ways must be found to permit ports

and harbors to continue the dredging of new and existing waterways to ensure

the safe passage of commercial shipping. He outlined a number of techniques

(clean material capping, borrow pit disposal, split-side disposal, deep ocean 4

disposal, hypersaline basin disposal, submarine canyon disposal, and erection

of offshore islands) for the disposal in the marine environment of dredged

material containing Annex I substances under the London Dumping Convention.

Ad Hoc Scientific Group Report on Dredged Material (Paraphrased), 1981

As a result of the Ad Hoc Scientific Group's considering the IAPH document at its intersessional meeting in May of 1981 in Halifax, Canada, the

Group rendered a report to the Convention.

There was general agreement that, while many of the special measures

showed promise for future use, there was very little information on the extent 4

to which the techniques would be successful in practice. The Ad Hoc

Scientific Group, therefore, agreed that dredged material (spoil) disposal

operations involving special care techniques should be conducted as field

research studies to gather experience with a view to allowing "special care"

measures to be used on a routine basis.

4

The Ad Hoc Scientific Group agreed that existing

regulations or the interpretation of the terms "trace

contaminants" or "rapidly rendered harmless" in

respect to Annex I contamination of dredged spoil

could be interpreted to allow national authorities to

evaluate research results and utilize, as appropriate, 4

208

4
"special care" measures in the disposal of dredged

spoil. These measures should ensure that disposal

was conducted in a manner which would avoid undesir--

able effects, especially the possibility of acute or - -

chronic toxic effects on marine organisms or human -

health whether or not arising from bioaccumulation in

marine organisms, and especially in food species.

The Ad Hoc Scientific Group, therefore, recommended to the Consultative Meeting that Contracting

Parties should take note of the possibility of using

"special care" methods as suggested by the IAPH where

disposal of dredged spoil contaminated by Annex I

substances is being considered. The Group also recommended that Contracting Parties should be invited to

submit details of any experience gained, with respect

to using these methods, to future meetings of the Ad

Hoc Scientific Group.

The significance of the issues raised was highlighted not only by the

attention that will be given by the Contracting Parties, but also by the

inquiry received from Mr. P. A. Haywood, Secretary of the OSLO Commission

(which administers the OSLO Convention, governing, the ocean dumping of

wastes, including dredged material, in the North Sea). Mr. Haywood attended

the Fifth Consultative Meeting in Londoc; as an observer for the OLSO Commission and expressed great interest in the IAPH position. He requested that

the IAPH furnish to him a copy of any statements which had been prepared

addressing these concerns, as well as any studies which may be available

(or which may be prepared) by the IAPH concerning the ocean dumping of

dredged material.

Sixth Consultative Meeting, 1981

Later, at the Sixth Consultative Meeting in London, in October of 1981,

IAPH additionally invited the Contracting Parties to express their views upon

the applicability of the "emergency" provisions of the Convention to the disposal of dredged material containing Annex I substances which may not be

within the "trace contaminant" and "rapidly rendered harmless" exception

provisions to Annex I materials. On the issue of "special care" measures, we

received support for the Contracting Parties by the acceptance of the recommendations of the Ad Hoc Scientific Group. At the same time, the IAPH confirmed its continuing interest in the consideration of "special care" measures

at future meetings of Contracting Parties and the Ad Hoc Scientific Group

and extended a continuing offer of technical expertise in matters relating

to dredged material. With regard to utilizing the "emergency" provisions of

the Convention, the delegates expressed a decided preference of using one of

matter the "special care" techniques proposed by the IAPH rather than consider the under the "emergency" clause.

209
Also, whil in London for the Consultative Meeting, members of the IAPH

delegation met .ith members of the International Association of fredging

Companies to initiate a cooperative joint effort. I am pleased to report at

this time that the work of both associations has led to developing a draft

for a "Dredging Reference Book for Developing Nations." The final proofs

will be availabi e for review in December, and we plan to have the book in

print in early !pring of 1983.

Continued cooperation between the AAPA Special Dredging Committee and

the IAPH Ad Hoc Dredging Committee is mutually beneficial and serves to

intensify the efforts of both associations. These two committees jointly

developed questjonnaires for all ports, worldwide. These questionnaires

were designed tq determine the effect of national and international legal

and regulatory controls on dredging efficiency. The final report, "A Survey

of World Port Practices in The Ocean Disposal of Dredged Material as Related

to The London Djmping Convention," was published in April, 1981.

Section 404/10 Regulatory Relief

Within the United States, experience has shown that an inordinate proportion of delays in granting dredging permits stems from a lack of an

urgency, or of ýaI law requiring an urgency, in completing interagency coor- ".

dination reviews within a reasonable period of time. In this respect, our

continuing efforts to cause reforms in the Section 404/10 regulatory programs

have been, partially successful. In January of 1982, the AAPA wrote to the

Vice President of the United States in his capacity as Head of the President's

Task Force on Regulatory Relief. In that submission, we emphasized that

environmental concerns should not be the overriding public interest factor in

issuing or denyihg a permit, that greater use of general permits should be

made in permittiig maintenance dredging activities, that interagency coordination provide for greater authority for the Corps of Engineers, and that

agency periods f r submitting review comments be reduced along with establishing a mandated period of time within which a decision must be made. In

May of 1982, the1 Vice President issued letter instructions to concerned (

agencies directing administrative reforms along the lines suggested and not

consistent with existing laws.

Hearings on the Reauthorization of the Marine Protection, Research and

Sanctuaries Act of 1972 (1982)

In June of this year representatives of A.APA again appeared before a

subcommitte• of the House of Representatives to voice concern in the direction

that the Comittee appeared to be headed in reauthorizing Title I of the

Marine Protection, Research and Sanctuaries Act of 1972. The Senate Environment and Public Works Committee approved a bill earlier this year to be

presented to thelfuli Senate that provided for a straight one-year authorization of the Marine Protection, Research and Sanctuaries Act. The version

under consideration by the House Subcomittee provided for an amendment that

esspntially would make the London Dumping Convention a self-executing treaty.

Treae'as are of two kinds; those that are self-executing and those that

require enabling legislation. The London Dumping Convention is not self210

4
executing. It was drafted in general terms for subsequent implementation

by signatory countries according to their rtational authorities. We strongly

opposed any "Convention Adherence" language being inserted as an amendment

to the Marine Protection, Research and Sanctuaries Act of 1972. To suggest --

a separate application of the Convention apart from the national Marine

Protection, Research and Sanctuaries Act would directly interfere with the

administration of a national ocean dumping program. Such a provision would

open the doors to innumerable litigation proceedings whenever one was dissatisfied with decisions and permit conditions rendered under the national

Marine Protection, Research and Sanctuaries Act program. .4

During the week of September 20, the House of R;,resentatives passed

H. R. 6113. In a supporting floor statement, a Committee member made very

clear that:

"Nothing in Section 5, or in any other provision

of the compromise version of H. R. 6113 tnat we bring

to the floor today is intended to change the nature of

the London Dumping Convention to accord 'self-executing' status to the Convention, or to obviate the

requirement for the Convention's legally binding provisions to be implemented domestically through pro- -'

mulgation of necessary rules and regulations. Currently

the London Dumping Convention and its annexes have no

iodependent status providing the basis for judicial

challenge of any action by the Administration or

Secretary, or of any recipient of a permit issued under

the act, beyond relevant implementation through the

act. This situation is intended to be unchanged by

H. R. 6113."

We were also pleased to learn that Representative Clausen, ranking

minority member to the Public Works Committee, further stated that:

"It is further the strong intent of the committees U

that necessary dredging and disposal of dredged

materials must continue in order to maintain the vital

flow of commerce through our nation's ports."

United States Environmental Protection Agency Ocean Dumping Advisory

Committee, 1982

In preparing for the Sixth "'eeting of the Ad Hoc Scientific Group on

Dumping that was held in Paris on September 27 to October 1, 1982, I had the

privilege to appear before the United States Environmental Protection Agency

(EPA) Ocean Dumping Advisory Committee on September 16 as representative of

the AAPA for the purpose of presenting the views of AAPA and encouraging -.

their adoption as the United States' position. These views will be discussed

in more detail, shortly.

211
We were not entirely successful in shaping the United States' position

to back those of the IAPH relating to the necessity or no necessity to develop

additional standards for the assignment of'substances to Annex I or II of the

Convention and relating to the use of "special care" measures in the ocean

dumping of polluted dredged material. However, the United States' position

as adopted did support the following concepts:

* With few exceptions, impacts of ocean disposal

of dredged material are mainly associated with physical

effects. These effects are known to be persistent and

often irreversible. The biochemical interactions,

however, are infrequent with no clear trends, and bioaccumulation of metals and hydrocarbons is usually

negligible. Furthermore, land-based altcrnatives

appear to offer limited additional protection in relation to human impact as compared to ocean discharge.

Most conventional land-based alternatives often result

in drastically changed geochemistry of the dredged

material with a subsequent enhanced release potential

of chemical constituents (especially materials such as

mercury and cadmium). .- ,

0 Dredged material containing Annex I constituents

or exhibiting Annex I properties can be safely ocean

disposed. Annex I constituents can be regarded as trace

contaminants through application of disposal site selec- "'

tion and management to minimize unacceptable adverse

effects. Ocean disposal can be carried out to prevent

hazard to human health, harm to living resources and

marine life, oamage to amenities, or interference with

other legitimate uses of the sea. This approach is

also in conformity with Aronexes II and III of the Convention.

* Highly contaminated and toxic dredged material 0

can be disposed of in open water if special care is

exerci:ed in site selection to ensure that the material

is isolated from the biotic zone and if the approach

involves significant disposal site management (e. g.,

capping, selection of an abiotic area).

9 There is no single disposal alternative for

dredged material disposal that is inherently suitable

for a region or a group of projects and there is no

single alternative, land or ocean based, that presumptively results in impacts of such nature that it can be

categorically dismissed from consideration or arbitrarily chosen.

212

0' +

A * -
Sixth Meeting, Ad Hoc Scientific Group, 1982

There followed in Paris in late September of this year the Sixth Meeting

of the Ad Hoc Scientific Group (AHSG) on Dumping. Our IAPH delegation again

attended in an invited observer status and participated in the consideration *-

of matters relating to dredged material. Our consultant, Dr. Willis E.

Pequegnat, presented an update regarding the experience of member nations in

using "special care" techniques in lessening the environmental impact of

disposing in the ocean dredged material containing Annex I and other toxic

substances. Several delegations questioned whether the use of "special care"

measures cculd properly fit under the "rapidly rendered harmless" exception

clause for disposal in the ocean as contained in Paragraph 8 of Annex I.

Additionally, they requested that the matter be referred to the Seventh Consultative Meeting in London, to be held in February of 1983.

Another major issue taken up by the Scientific Group at the recent -

meeting in Paris was the question uf need for developing additional criteria S

for classifying substances to Annexes I or II of the Convention. The Ad Hoc

Scientific Group decided to make a stronger effort to develop additional

criteria. Considerable support was expressed 'for the adoption of "numerical

standards" for classification purposes based upon laboratory toxicity testing

and bulk sediment analysis. The application of such standards to dredged'

maceriaI could have disastrous effects upon this country's ocean dumping

program. It would threaten an even greater "overregulation" of dredged

material--in disregard of the known characteristics of sediment that mitigate

the effects of any Annex I substances that may be present. In Paris, we

emphasized the different treatment that should be given dredged material. In

recognition of these port concerns, we understand that the Scientific Group

will invite IAPH to submit a paper addressing the special characteristics of S

dredged material and explaining the different treatment that is warranted.

This affords an excellent opportunity for ports to affect the future treatment of dredged material under the Convention before action is taken by

Contracting Parties. Any action taken under the Convention will, of course,

have direct consequences in this country, since adherence to the Convention,

as promulgated by national laws, is required under the Marine Protection,

Research and Sanctuaries Act.

Preliminary discussions at the meeting resulted in the EPA Committee

on Ocean Dumping concurring with the preparation of a report and joining

with the Ad Hoc Scientific Group in requesting that AAPA and IAPH jointly

prepare the report in time for consideration at the next meeting of the

London Dumping Convention during the period February 14-18, 1983.

Funding the Future

As in everything these days, availability of money always is the first

hurdle. We at AAPA and IAPH have held discussions with the Director of Ports .

and Intermodal Development, United States Maritime Administratioi.--hoping to

come forth with a grant of approximately $10,000 t3 partially cover the cost

2

213

•S
of the requested research that is to be completed between now and February

14, 1983. In the meantime, we are reviewing closely our projected program

and budget at AAPA.

Turning ba'k the clock to June, 1979, and early 1980, the incipient

years of the Special Dredging Committee'L existence, we find that the Port'.

of New Orleans supplemented the initial $10,000 of "seed monies" provided.

by the AAPA general fund by the amount of $22,357. This total of $32,357

provided sufficient funding for those early organizational years. With the

organizing and early on projects, there soon developed a need for additional

funds--and they were to be raised through voluntary fund-raising efforts.

Since logging in our first contributed funds in September of 1980, the AAPA

Special Dredging Committee has raised $147,800 as of October 15 of this

year. We are particularly grateful to the International Association of

Ports and Harbors for contributing $10,000 to our account in September of

this year. On August 11, 1982, the Secretary General of IAPH released his

second fund-raising letter request, funds from which will be applied against

expenses to be incurred during the year that started in October, 1982. Concurrently, the AAPA Special Dredging Committee is under way with its own

fund-raising program to cover an estimated $23,000 shortfall during the

coming year in its program and budgeted support of AAPA and IAPH activities.

I might add that the International Association of Dredging Companies contributed through the IAPH $2,500 this year and has pledged an additional

$2,500 this coming year. At this time, our AAPA program and the IAPH

Dredging Committee Ocean Dumping supporting efforts are running $40,000 to

$60,000 per year.

0

IN SUMMARY

Summarizing 1982 to date, the AAPA Special Dredging Committee has continued to emphasize direct liaison with concerned members of the Congress

and officials of the United States Army Corps of Engineers as well as other

federal and state agencies and officials with an interest in or control of

dredging laws and regulations. We are actively seeking the opportunity for

any forum at which we can present our problems and suggest the changes in

procedures and testing that are necessary. Our support of IAPH and IAPH's

support of our activities of mutual interest have been most beneficial. We

have been successful in publishing our position in magazines read by the 0

dredging, business, and port industries and have been able to attend and 7,

participate in meetings and ,onventions representing elements in a position

to influence our objectives

We look forward to an even more productive year in 1983, and an even

closer relationship with our counterparts in Japan.

214

S. .I . i a I I 0

i | | a . .. . 1
SOIL IMPROVEMENT BY DEEP CEMENT CONTINUOUS MIXING

METHOD AND ITS EFFECT ON THE ENVIRONMENT

Tadashi Otsuki

Masanori Shima

Japan Dredging and Reclamation

Engineering Association

INTRODUCTION

Since the coastal area of Japan, where the bulk of Japan's inaustrial

areas and populations is concentrated, is mainly composed of soft alluvial

clay, it is important to know how to improve the soft clay deposits. For

this purpose, various oil improvement methods have been developed and practiced. In order to achieve rapid construction of structures with heavy super

structures and to meet environmental restrictions which are strengthened year

after year, new improvement techniques are needed.

The deep cement continuous mixing methcd, called "the DECOM" in Japanese, was developed for this purpose. This method is based on cementation

rather than the usual concepts of consolidation, drainage, compaction, and

replacement. Since the DFCOM method enables rapid stabilization without

pollution, many soil improvements using this method have been conducted.

In this paper, the problem of how to achieve the quality between previously improved and newly improved zones, called "the overlapping problem," is

discussed as well as the effect oF DECOM on environmental conditions using

field measurements from Yokohama Harbour (Photo i).

/I

Photo I. Yokohama Harbour

215
OUTLINE OF THE DECOM METHOD

In this method, slurried cement is injected into the ground and mixed

with soft clay by rotation, lifting and lowering the mix.er, while soft clay

is hardened through hydration between hardening material and water. Then

pozzolan reaction between hydration material and clay material is progressed

and clay is cemented through these processes.

"1he DFCOM method has many advantages:

a. Strength is achieved by controlling the hardening annex ratio according to the properties of the clay to be improved.

b. Strength is rapidly obtained, which enables rapid construction.

c. Deformation is very small and the effect on super structures

negligible.

d. Soft clay Is hardened In the field tinder low vibratory and low noise

conditions; pollution is minimized.

v. Hvge amounts of sand required by conventional improvement methods

are not necessar%,.

Delayed_ Ryactingce mynt

The reaction rate between clay and cement is so rapid that the quality

of contact betwen the previously improved and newly improved zone' is less

rvliible when improved work ceases due to weather conditions or machinery

t robles. In order to solve this problem, a study was conducted on dtlaved

reaction hardening material. In the first stage, delayed settling material

was ;tudled and it was concluded that there are problems in its efficiencv

and cost. In the second stage, a study was conducted for a material that

enrihbIs delayed hardening at the first stage bit ,ichieves the proposed

strength it the final stag, of t - 90 davy. A 4ood result was obtained in

the laboratory And was certified in the field. 1he next section of this

paper di sts-.ses laboratory and f.eld test resuilt: obtained for this newly

developed hardening material.

Lihoratory r..t I- Results

ihe reqtu I remen t s for t he ma* er Lal are stimmar i zetd below:

a. ;Harde~nin takes pLice after ) da~,• of mixing.

h. Vnconi itdt't] comrprtss ion strength, qu, at t )40 day.s Is eItal to or

mor, than 30-,4() kg.'c:m,-

Q. ;he cost i ; in in allowable rang,,e.

2 lb
Retarder

Normal portland cement has generally been used for DECOM because it is 2 easily obtained. However, setting time of this material is short, within

10 hours. In order to delay the setting time, an investigation was carried

*" out for marketing to special goods. The results are summarized in Table 1.

As indicated in the table, retarder did not satisfy the requirement under

conventional annex ratio. It is of course possible to achieve the requirement when cost is not considered, but this method is not practical. From this

consideration, it was determined to develop a method which enables delayed

hardening of cement without the addition of a retarder.

Table 1. Results of Delayed Setting Tests

H arden ing

Material Annex Annex Ratio Setting Time

non 0. 6h 40 min.

0.25 7h 10

A 0.40 8h 00

0.60 8h 30

0.80 8h 00

0.25 ;h 35

0.50 8h 40

"0.30 8h 20

p C 0.45 6h 30

Normal 0.35 7h 10

portland D 0.50 6h 15

cement

w/c = 150% 0.20 6h 20

E 0.30 6h 30

N 0.20 5h 30

F 0.40 8h 25

0.60 8h 35

Delayed Hardening Material

A study for delayed hardening cement began in 1978. Two methods were

noted:

a. Use of clinker material which provides a longer setting time.

b. Use of material with higher pozzolan reaction, which also enables

longer setting time.

In a series of laboratory tests, both methods satisfied tie requirements.

Consi,'ýrlirg the lower cost and ease of manufacturing, method b was tested

fur tic :, and the material indicated in Table 2 was developed.

217
"fable 2. Laboratory Test Results for Newly Developed Hardening Material

11ardeninvgAnx etn Unconfined Corn. u_ (kg/cm 2

Water* Aneretn emp. 7dy 1 a 8dy 5 a 1'a Material Ratio Time7 a 14dy2dy56ay9ly

15 3 00 C 0.9 7.0 16.8 22.4. 24.7

sea- (200 kg/cm 86Sh 30 1.6 9.3 25.9 32.5 37.2

D)M se t waterw/c=0.6 20 3 bil 20 11.7 20.1 36.1 46.4 5.

(273 kg/cm ) 30 11.0 725.6 47. 49.1 5.

WA -/ wat~er/cement (weight ratiol

seawater is used for water above. .

1his ma. -ria. is a kind of I~ tm

ct.ment mixed withI an inorganic _____is%___

mater ial and Is harmless. [hle rp 0F07 IS 30

de'laved hardening p roesses ~;

Ot thfis material are suggested 2 as lol lows -

7 2 4 4 91

T~. Is,.

L) fiII h .-.i+-+ in liIqui d phase i.s requi red for hardening. When 'thle amoullt

of ckc!,.nt is small, the time to ensure hardening is long. Tn addition,

the hardoning t ine is oft en further delayed by mixing material that

hinlders the d1is';olViTng rate.

") M'finvu maiter ial *which conta ins material that hinders hardening, slowly

reactS With Clay, and hardening slowly prog!resses.

"o fardohn Icc t imt of c lay is cont rolled by changing the mixinv rat.io when

tht newly; developed maten lal is used. Hardening time also depends on

Water content andl orgýan iC Content of tile clay.

" Aiter hyvd rat ion heg ins, st rengt h of the c lay' is~ significantly increased

wio I tidc tion of C(Xi (1)-' and thermal hydration associated with t he

1) r cci' 

o l'.d~stIonprtdtzcts are mainlv i-alc iun silicate and caic him -iultminato

t'.-drate , wh ic citre ;Lab~le for long per iods of t ime.

tc imi l icat od triteo c han %c t o t hte more stablo mater ialS.

vi 1ehr~rc te inti xonotI It w Wit h t i inte.

tIa~n ric ct i n ti hi clIiv wIlI cont I ito f or ai 1tnst ime and p roduct's4
i/

Field Studies

Field studies were conducted 4-

offshore of Daikoku-cho, Tsurumi-ku, Daikoku bra.

Yokoham City (Figure 1) from September

1981 through March 1982.

\ -harf -,ko'it 

Prnposed ,te

Figure 1. Guide map for the site

Soil Conditions

Before improvement, a soil investigation was carried out at a point

shown in Figure 5 and the results obtained are presented in Figure 2. The

properties of the clay are summarized as follows:

water content

w = 50% - 90%

unit weight

ty = 1.5 - 1.6 g/cm3

unconfined compression

strength, qu

2b

qu 1.15 + 0.54 z t/m 2

(z =0 at -15 m)

219
,.. = N V'alues

100

30- •'

35T

• ". r='•i•"===so _,.

Figure 2. Soil conditions at the site

Machinery Used

The DECOM No. 2 Barge was used in this field test. This barge was manufactured to prevent sea pollution and noise as well as provide easy operation.

Design Criteria are:

Wave, height : 1.0 m

Wind velocity : 15 m/sec j

Current velocity : 2 knots Work Conditions

Allowable incline : at Trim

1.5 0 at Heal

Dimensions are as follows:

a. Hull

Length : 60 m

Breadth : 30 m

220
Depth : 4.5 m

Tower height (above the Upper Deck) : 66.2 mi

Draught (Design) : 3.4 mi

Displacement (Design) : 5,800 tons -

Accomodation : 2 (for two people)

7 (for four people)

Meeting room : 1 (for 20 people)

b. Mixing equipments

Mixing shaft : 4 (rotating)

Center shaft : I (fixed)

Diameter of mixing wing : 1,800 mm

Mixing motor : 900 KW x 2 set

Deep cement winch : 36 tons x 2 set, at speed of 0-16 m/min

Anchor winch : 6 30 tons at 1 m/min for construction

15 tons at 18 m/min for barge operation

c. Slurry - Plant

Silo for hardening material : 400 tons x 4

Slurry mixer : 3,500 Z x 2

Slurry agitator : 18,000 Z x 1

Slurry injection pump : 600 O/min 6

d. Engine

Main generator engine : type NKK-SEMT-PIEL STICK

S.H.P. 4,500 PS

Revolution 514 r.p.m.

e. Electric installation

Type : Horizontal, deep-proof, separately ventilated,

revolving-field, salient-pole type AC generator

Output : 3,750 KVA (3,000 KW)

Voltage : 3,300 V

Frequency : 60 HZ

Revolution : 514 r.p.m.

General arrangement of the DECOM No. 2 barge and flow of plant are indicated

in Figures 3 and 4.

221
23 op. room.

j! mix. m~g

1-41

Figure 3. Outline of the DECOM Barge 2 -

Bucketele~sor Buket ele~ator

Silou

Figesuren 4.Flwof p1ing,

Silo si aSilo Sil

222ato

------ --- - - - - - - -
Specification for Soil Impcovement

2 The area of an improved pil'e is 9.48 m and 6 piles were constructed in

one cycle under the spacing shown in Figure 5. The sequence of improved pile

is shown in Table 3 and the connection of each improved pile was conducted

using 5 methods within 96 hours.

33o

Figur 5. Sp c n of im r v d i e

-4-°

• .• i•~~~---.--', • -. '

33 30 0 '

Figure 5. Spacing of improved piles'"

Table 3. Sequence of Improved Pile

Penetration No. of Imp.

Date Pile Test Conducted

ist day No. 1. 2 _'_'.

Jnd No. 3 connection after 24 hours

3rd No. 4 48

4th No. 6 72

5th No. 5 96

'A L - 0.

• m,n .m 230.

Specifications for improved

piles are shown in Table 4. As

shown in Fic:ure 6, slurry cement f was placed during penetration and -:,,,I

t hen m i xed with clay by lifcinthe mi-xinc win,,,.

\, k .nd r,•snj,. 2 0n"

2(

Figure 6. Sequence of improved pile operation

223
Table 4. Specification for Improved Pile

Items Specification

Penetration speed 0.50 - 0.25 (m/min)

Withdrawal speed 1.00 - 0.50 (m/min)

Rotating rate 20 - 40 (r.p.m.)

Improved depth -18 - 52.0 m (DL)

The composition of newly developed hardening material is as shown in

Table 3. Two methods, 210 kg/m 3 and 160 kg/m 3 , were adopted. Water-cement

ratio was 60% for each method using seawater.

Table 5. Composition for Newly Developed Material

Composition (a) Pile No.

210 kg/mn No. I DM set 160 kg/m No. 2,3,4,5, &

Results or Field Test

7he field test results are as follows:

a. Construction quality

o Torque of mixing apparatus

Torque induced during mixing is summarized in Figure 7. The

torque during penetration was smaller by 100 - 200 amperes (A)

when compared with that induced using normal portland cement.

This difference during w4.thdrawal was significant reaching 150 -

600 (A) and was caused by rapid hardening when normal portland

cement is used. The torque indicated a value of 100 to 200% of

allowable capacity in the use of normal portland cement. On the

other hand, the torque in the use of newly developed material did!

not reach 100% except when penetration reached a hard layer with

N values more than 50. In addition, the torque for the connection

part did not show any significant difference within 96 hours.

This demonstrates the efficiency of the newly developed material. -

o Loading to mixing apparatus

Loads on mixing apparatus are summarized in Figure 8. The same

torque trend was observed. The load when using normal portland

cement suddenly decreased at around -40 m in penetration, and

significantly increased reaching 560 - 620 tons which exceeded thel

self-weight of mixing apparatus (480 tons) in withdrawal. In

contrast, the load when using newly developed material was within

the self-weight, regardless of time of 0 - 96 hours.

224

I I
IDM

. 00 L.

S41--

Sind. 24 -

cmt.

Stnd. cmt.

.50 "• ol~j/•Cement -Normal portland

.1 j I __ " 0 -10 -20 -3 0 -II0 -5t -so -40 -30 -20 -I0 0

penetration - - thdraal

m.proced depth"

Figure 7. Torque mobilized dui g operation plotted versus depth

600I- 

" 1

~0C __ I __set_ A 72-

40C Sind. cmt. 0 _ _.. "-d"- ,'

2 -L__ ____ __ Stnd. cmt.

I - Normal portland I

* ml cement 100 , _______

0 -10 -20 -! 0 -40 -50I-50 -40 -30 -20 - P•,etration , thdrawal "

_mpro_,"'_ _ pth, m_ _ _ ---- 6

Figure 8. Load mobilized through operation versus time

O

225

/ -
S/

• o,

'°. R

o Accuracy

In the DECOM method, improved piles were constructed by overlapping

to make the ground a unified improved body. Therefore, accuracy

of construction is an important checkpoint. Figure 9 indicates

the connected conditions, and the barge location is determined

by transit survey. The location of.the mixing wing was measured

using an automatic inclinometer. From Figure 9 it can be

observed that reliability of the connected zone is high enough

regardless of time (0-96 hours) when the newly developed

material is used ...... Q-'

0 hrs. 24hrs. 48hrs. 72hrs. •hrs. t",,"

-20 •

- a.__9o • /q-7

-40j ! • •. :'•.:

°

•)'."

Figure 9. Connected conditions between piles versus time •"[•-'[

b. Resul=s obtained from check boring and soil test i•[•i•![

o Results of check boring "•,--.

€

Continuous sampling was conducted at 5 points shown in Figure I0 , • ,

to certify the connected condition and the physical and strength '•'-

properties of the improved soil. Of the 5 borings, two were •#•

inclined (one for the check of connected conditions). The results •,• •

obtained from the inclined boring are shown in Figures ii and 12. ,,_•." .

As shown in the figures, the connected zone is unified regardless • •

of time (0-96 hours). "-'•

"2•721•2

S........ . £

"-"2.1"

0

//

//

/

, ! !
i iencline

.0

30'0

Figure 10. Loatonooscek boingl

1 ,nece \7 cooneeteed

Uens shaft er dh afe 48hhr..

nc ieis,~ . cr1~ cracv-Hx

Ies' sape5-4 lensed shaped

7'i cracks

Actutal in. 15.

Figure 11. Inclined boring (No. 1) Figure 12. Inclined boring (No. 2)

o Water content and unit weight of improved soil

0

Water coi tent after improvement ranged from 40 to 80% (Figure 13)

and indicated smaller values by 10-20% than the values before

improvement (w 5C--90% before improvement). On the other hand,

unit weight after improvement did not show any significant difference than before improvement (Figure 14).

227
Vat•-r content %V( UnLit -eight 47, dWma'

40 50 60 70 80 90 1.4 1.5 1.6 1.7 1.8 -

I.S7

-20 0 after o.2 2 -20 

A No. INa bifore N. 1

8 * before

- -30 -30

is o

-40 0 . -40 0

-50 -50

Figure 13. Water content versus Figure 14. Unit weight versus

depth depth

o Unconfined compression strength - _ i ..- /

In Figure 15, unconfined ( m, (DL , f0 2 5 00. S t 0 o0110 -'20 50 1 40

compression strength before

and after improvement is .

compared. The values of "

qu are those after 3 months "0 

of improvement. The values 10.0 -24.0 °

of qu fok a = 160 and *=164 at' I 0 _-=_o

210 kg/mo were 56.9 and

75.4 kg/cm2 respectively.

Those values satisfy thý 20.01-34.0 o =2I .kg, m -

design criteria. o@ -

40. Q -54. .... . .

Figure 15. Unconfined compression

strength plotted versus depth228 -.

6*4 i
i

c. Temperature of improved soils

A thermometer was installed at three depchs: -19.8, -22.3, and

-24.8 m of No. 5 pile. The results are presented in Figure 16. A

significant difference can be observed in temperature of the soil

improved by normal portland cement and the newly develop'ed material.

The temperature 0 0 of soil treated with the new material rose slowly, 0

reaching 40 -48 after 2 weeks, whereasla temperature of 45 was measured after only 1 day when standard lportland cement was used.

SXN Cmt.

-Normal p rtland

___... _ _____.] ~c

SI 3 3 4 I , 9 I* II I3 ] 4 I$ N 1 6

it

Mossurem~t dav

Figure 16. Results of temperature measurement

EFFECTS ON THE MARINE ENVIRONMENT

Water Quality and Sediment

The water quality and sediment investigation was conducted in March 1977

in Tokoyo Bay (Figures 17 and 18). Items covered during the investigation are

listed in Table 6.

Meteorological and Oceanographical .... tions

Resu.ts observed about the -,,eral meteorological and oceanographical

conditions were as frolows:

Weather

The weather was e'ther cloudy or fine.

Wind

Direction and velocity of wind were E - NE and 4.4 - 5.8 m/sec

(4.8 m/sec average).

0 Temperat ure

1'he air temperature reached 11 low of 4.3 C before carrying out and 10. 1 -

15.40C during and after. Water temperature reached a low of 7.b C before and

8.8 - 1O.6 C during and after.

229
Arantitimetiotior.

Tokyo 1ok b ay

f~ f fT okyo 

N

inve5I.(gat ion

F i gi ir v 1 7. ocat io of n i nfv e-t i g;it i on

2 30
N

Bi B2

As4 

A2

0 .

PROPOSA&L SITE

Figure 18. Stations of investigation

CurrentBefore operation the current velocity was 0.04 - 0.15 m/sec (0.10 m/sec

average) and the direction of current was nearly NNE. During operation the

velocity was 0.01 - 0.11 m/seec (0.06 m/sec average) and the direction was

nearly ,.

i)5ej'_th!

Mie sea depth in the investigation area was 7.0 - 10.2 m (9.0 m average).

Wd t vr "

Water quality results were as follows:

I.rna.r\-jl ren cv

,,efore operation tihe transparency values were 1. 10 - 1. 35 m (1.25 m"

av(roe ); 2 hours aftel operation comm~encement low values of 0.8 - 1. 30 rn

1,.1) rn av.0rit occurred -nd offects bv the operation were recognized.

H•, '-r, .- soonti a ttr thi valies recovered to 1.20 - 1.50 m (I. 30 M, average).

A.~r i.d~t Iv

r!,Itd t mrt..iuri•'mnts ari, showm in Figure 19. Before operation tile

,rW!, ti'i r.i','r "! '..I qn ,it the' ii 'er layer, 3.,) ppm ait the middle laver,

,vt opm it iht, 1,•r lIv.'r. A\t 2 and A hours after opert tion the ne~irer

, ,' t i:,t im stIti(,s wort* to tile proposal site, thi highcr values they

231
!

00

DON

ElU

Lo

SA

4'n

". -0 

0

05.

0.

0 u

0.

0 Aj

0 4, 

I

Aj,

0 ;.

2 2."

0~

6-4.

,44 4

~10 U

Id~ L-4

CD230
r_0

0l 0 (3 -0 A 00

0 40 0

0, z 0 0 v

03 0

e-. 0 0 a)

a)) a"W0 JS4

m4 .0f-J0

ON

00

-4 U)o

0- 0

U 0

x - ZI , 00 9.r

Q- d) -4 u

0-4 r. 1. 2. 4 IJ -,4

4~ w M (U(U ) (1) 120 U

zi 1 ~ 0-42J 0 i= Ia

o *12 2.~--4 -4 C14 2.40 

0 -IC40 C) 0 m 0

0 (1)*4 *01tic

0 0 1) -'12~J 0 12 dLi U-4 U ~ U r_ 00.~1 000-0 J 0.JJ2J-4

*L 2- 1r42 0 .J . ~ ( ý4E~ - 24-

:I . dJ *1J 122.1 J-. WlC

u 0 A

(if, 0-44

I 233
showed, over 4.0 ppm at 0 m (St. 0) and 50 m (St. Ao) on average. Furthermore,

the upper layers showed higher values of 4.1 - 5.6 ppm. The middle and lower

layer showed lower values of 3.0 - 3.5 ppm and 2.0 - 2.6 ppm, respectively,

not much change when compared with before operation values.

SS (Suspended Solids)

Before operation SS values averaged 5.0 ppm, 3.3 ppm, and 4.3 ppm at the

upper, middle, and lower layers, respectively; however, during operation SS

concentrations increased about 1.0-2.4 ppm for the upper and middle layers.

Simultaneously it was recognized that 2-3 ppm increased at each layer near

the proposal site. One hour after operation the values returned to the

before operation values at every station and layer.

pH .

The pH results are shown in Figure 20. Before carrying out pH reached a

low value of 7.6 at the proposal site; this value did not satisfy the environmental criteria in this sea area. However, at stations other than the proposal

site, pH values averaged 8.1-8.3. At 2 and 4 hours after operation commencement and 1 hour after operation the average values of 8.0-8.2 were generally

observed. A tendency was recognized for higher values to appear at middle and

lower layers than at upper layers and for higher values to appear at 2 and

4 hours after operation commencement than at 1 hour after operation. Some

effects caused by the soil improvement method were recognized.

COD (Chemical Oxygen Demand)

Before operation COD values averaged 6.2, 1.5, and 4.4 ppm at the upper,

middle, and lower layers, respectively. At 2 and 4 hours after operation

commencement the COD values of 2-2.6 increased mainly near the upper layer

at the proposal site (St. 0) and station of 100 m (St. B ). At the lower

layers changes were scarcely recognized.

DO (Demand Oxygen), BOD (Biological Oxygen Demand ,.n-Hexane Extract

Both before and after carrying out the values of DO, BOD, and n-Hexane

extract showed, respectively, 7.2-7.6 ppm, 2.7-3.5 ppm, and below 0.5 ppm;

the changes were scarcely recognized.

Sediment

The values of COD and ignition loss had scarcely changed after carrying

out. However, the tendency was recognized for the values of pH and water C

volume in bottom mud to increase from 8.2 to 10.8 and from 138.9% to 240.1%,

respectively.

234
41b

4)0

144LJ

0.

4) ý

0 C

0$4

z ('4

Cl.00

0 0

4) 1-

41'

10 r

0

4 ) ýJ cm-.4

0 C%4

Cl

4-i>

ý4 7

.0 0

A4)

0) In

0.

0 E -0

235
Discussion

Results obtained in this investigation indicated that the effects by this

soil improvement method (DECOM Method) were approximately as follows: 1) new

additional turbidities of 1-2 ppm, and 2) rising values of pH of 0.4-0.6

surrounding the proposal site.

T ese effects were mainly caused by: 1) stirring up of the bottom sediment

into tte upper layer by the mixing wing, 2) stirring up the bottom sediments

by moving the mixing shaft in continuous operation, 3) outflow of bottom

sediments and cement slurries attached to the shaft and mixing wing when pulled

up fron the bottom for removing, and 4) outflow of bottom sediments and cement

slurries attached to the shaft and mixing wing when washed after operation.

Ftrthermore, pH in the upper layer of bottom sediment showed a 2.6 rise

which %as believed to be caused by the soil improvement method itself using

cement slurry.

These effects, however, were mostly temporary and disappeared soon after

carryi g out. The pH values 'n the upper layer of bottom sedime-ts certainly

returned to the values before carrying out after about 3 months.

Noise

Noise from the DECOM-I barge was investigated in November 1977 in Tokoyo

Bay.

This investigation was carried out at 5 stations on the vessel and

I stati n on the sea. All engines of DECOM-1 barge were in operation. Consequently, the levels of noise were about 80-90 dB on the vessel and 67 dB

on the sea 50 m distant from. the barge (Figure 21). From data obtained in

other sea areas, the noise levels at distant stations were approx.;._nately tO65 dB alt 100 m, 55-60 dB at 200 m, and 40 dB at 1000 m.

Ihuse results showed that the value measured at 200 m satisfied the

criteri4 of noise levels of 60 dB in a dwelling area.

SU.NARY AND CONCLUSIONS

A Series of laboratory and field tests for soil improvement using the

newly developed hardening material were described as well as the effect on the

marine environment. flhe following conclusions and suggestions are made from

this st dy. %

(I Because of delayed hardening of the newly developed material, it was

fouin: t Ia t a connec ted condition of suf f ic ient qual it y can be achieved even if

const ructed 96 hours after the previous improvement.

-4

236

I

. " , .o . • , o .. . . .. • • . . ° . - . . . . . ° . . .° . . .. • , . , - - . .
)e-CM-! vpessel

()67)

Mixing wn

1T ( 72)

S25.00

Figure 21. Stations and results measured of noise

I 6 : stations ( ): results (dB))

(2) Therefore, the severe time requirement to connect the zone within one day can be loosened. The coefficient B , which indicates reliability of

the connected part, can be expected to have a larger value than conventional

values such as 0.5 - 0.6 (for the type of slurry jetting through withdrawal) and z 0.8 - 0.9 (for the type of slurry jetting through penetration).

* (3) Unconfined compression strengths of improved soil treated with the

newly developed material where 56.9 kg/cm2 (A = 160 kg/cm3 , t = 90 days) and

75.4 kg/cm2 (i 210 kg/cm2 , t = 90 days). These values satisfy the design

criteria.

(4) It was also found that the soil improvement with this material did

not significantly affect the marine environment.

(5) It can be concluded, therefore, that the DECOM method with the newly

developed hardeninv mat.2rial has various advantages over the conventional

portland cement method.

237,
A COMPARISON OF METHODS FOR ESTIMATING

NUTRIENT RELEASE FROM LAKE SEDIMENTS

Hasaaki Hosomi

Mitsumasa, Okada

Ryuichi Sudo

Laboratory of Freshwater Environment

National Institute for Environmental Studies

ABSTRACT

This paper discusses four methods for estimating the

rate of NH -N release from sediment. Precision of the

4

NH 4-N release rate determinations was compared by ex-'

amining the variances among the laboratory sediment core

method, the in situ sediment core method, the in situ

chamber method, and the mathematical model method.

The in situ core method reflected the least precision

of the NH -N release rate determinations.

4

Statistical tests showed that the NH4-N release rates

calculated from the NH4-N gradient between the overlying

water and the interstitial wate.r of the 0- to 2-cm layer

(AZ= 1.0 cm) in the uppermost sediment did not significantly differ from lthose estimated by the Laboratory core

method and the in situ chamber method.

The mathematical model calculating the NH4 -N gradient

between the overlying water and the interstitial water in

the uppermost layer of sediment could well be applied to

other lake systems.

I NTRODUCT ION

We cannot ignore the effects of nutrient release from bottom sediments,

particularly in shallow lakes, on excessive growths of algae in lakes.- 3

Although many lake restoration programs, such as wastewater diversion and

advanced wastewater treatments, have been implemented, water quality has

not been Improved to the desired level in some lakes because of the nutrient

release from the sediment. 4' 5

238
S~/

In implementing lake restoration programs or eutrophication control

programs, it is necessary to quantify the magnitude of nutrient release from

lake sediments.

The methods for estimating nutrient flux from lake sediments are classiflied into two types. In the first type, nutrient flux is estimated from

the measurement of the rate of increase in nutrient concentration of overlying waters in artifically isolated in situ or laboratory sediment water

5-13

systems. In the second type, flux is calculated from Fick's law, i.e.,

flux is proportional to the gradient of nutrient concentration at the sediment- 4

7,14 water interface.

There are three methods of'the first type: laboratory sediment core

method, in situ sediment core method, and in situ chamber method. The laboratory core method is designed to simulate the lake bottom as closely to the

natural conditions as possible and to measure the sediment-water nutrient flux..4

In the in situ sediment core method the sediment-water nutrient flux is measured

by using the sediment cores placed near the lake bottom. The in situ chamber

method is designed to isolate a portion of bottom sediment and its overlying

water by an in situ chamber and measure the change in nutrient concentration

of its overlying water. 4

Many studies have reported the rates of nutrient release from the sediment using one or two of the above-mentioned methods. However, the precision

of the methods for estimating sediment-water nutrient flux has not been evaluated. In this study we quantified the magnitude of the sediment-water nutrient fltiy using the above methods and compared the precision of the methods.

MATERIALS AND METHODS

Study Area

This study was initiated to investigate the sediment-water nutrient flux

in Lake Yuiioko, a dimictic lake located in Nikko National Park. Table I shows

the morphometric data in Lake Yunoko. Intensive limnological monitoring and .,.

Table 1. Summacy of morphometric and hydrologic

characteristics for Lake Yuno.j

Parameter Lake Yunoko 0

2

Surface Area of Lake (km)

Lake Volume (m3 ) 2.62 x 10

Mean Depth (m) 7.4

Maximum Depth (m) 14.5

Length of Lake (km) 3.8

Water Retention Time (days) 40

239

- /•

,1 .
.,

modeling efforts have been conducted to assess the response of the lake to the

advanced wastewater treatment aimed at phosphorus removal, the ban of phosphorus detergents, and the dredging of a part of lake bottom sediment. 1 5'1 6

These investigations have revealed Lake Yunoko to be eutrophic. Chlorophyll a .

concentrations often exceed 20 i.g/Z. Total nitrogen and total phosphorus concentrations in the epilimnion range from 0.2 to 0.8 mg N/i, and from 0.02 to

0,10 mg P/h, respectively. The study station, shown in Figure 1, is 8 m deep.

In this investigation, NH4 -N release rates were estimated at this station in

August of 1982.

Lake I

Lake Yunoko

Odobu River

Shiranezawa River

Yumoto Wastewater 4

Treatment Facilities

Study Station

. 10

Lake Cen

12

0 10O0 200--

X__ _ Yutaki Falls

Scale, m

Figure 1. Location of study station and bathymetric

map for Lake Yunoko S

240

S
Laboratory Sediment Core Method

Sediment-water nutrient flux is estimated by measuring NH4 -N concentration in the overlying water of the sediment core placed in the laboratory.

Sediment cores were taken with the coring device shown in Figure 2. The

sediment core was placed in the dark and its ambient temperature was maintained within -2*C of that of the lake bottom where tht core was taken. Dissolved oxygen concentration was maintained close to that of the lake bottom

by passing mixed nitrogen-oxygen gas with various ratios through the overlying 0

water. The apparatus is shown in Figure 3.

Water temperature and dissolved oxygen in the hypolimnion during this

investigation ranged from 100 to llfC, and from 7 to 8 mg/1, respectively. In

this study, water temperature was maintained at 10C ± 2*C. Aerobic condition

was mairntained by passing compressed air through the overlying water. S

The overlying water was periodically sampled using a syringe from the

upper part of the core, and then filtered through a glass-fiber filter

(Whatman GFC; pore size = 1 jm). The filtrate was analyzed for NH,-N.

417

Ammonia was determined by the automated colorimetric phenate method. The

filtrate of lake water taken at the study station was added into the overlying -

water to compensate for the decrease in the volume of that after sampling.

ValIve.

Stainless Steel

'Wing

S 100 1000

. Lead

Attachment Conjunction

Plexiglass Corn Tube

'_.

Figure 2. A coring device

241

S

. ..
0

Nitrogen-Oxygen Mixed Gas SI~~~0-15 ml/rain. ..

Flow Meter -,

Fritted Glass Aerator

/Thermos ta t

__ Sedmet Core. --

Figure 3. An experimental apparatus used in the

laboratory core method

The cumulative amount of NH 4-H released from the lake sediment to the

overlying water at each sampling 4as calculated by

n

V(Cn- Co) + v(C -Ca)

A (1)

where r = the cumulative amount of NH4-N released from the lake sediment

2 3 -

(M/L )*; V - volume of overlying water of the sediment core (L ); Cn =NH4-N

3 concentration at n'th sampling in the overlying water (M/L ); Co = initial

NH -N concentration in the overlying water (M/L 3); v = volume of overlying

4 3

water sampled for NH -N analysis (L3); Ca = NH -N concentration in lake water

4 3 4

added into the overlying water (M/L3); and A = area of sediment-water inter2

face of the sediment core (L). .. ,

NH 4-N flux was estimated from the rate of increase in the cumulative _

amount of NH4 -N released..

In Situ Sediment Core Method

Nutrient flux is estimated by measuring NH.-N concentration in the overlying water of the sediment core placed near ia~e bottom. This method is

similar to the laboratory sediment core method. However, neither the dissolved oxygen control nor the mixing of th, -verlying water by passing the

mixed gas were conducted in this method. -

* M = mass, L = length. .

242 -.1

.1L-

? 71
I

Sediment cores were periodically pulled onboard. A portion of the overlying water was sampled after the overlying water was mixed hcmogeneously.

NH -N was determined the same way as the laboratory core method.

4

In Situ Chamber Method

The in situ'monitoring of the sediment-water nutrient exchange process

is performed using a submerged chamber as shown in Figure 4.

Capillary Tube to

Surface for Sampig yon. Rope

Port Vinyl Chloride

IS

-,

*580 0

500 -4Cuttig(Ed)

Figure 4. The submerged chamber used in the

in situ chamber method

Chambers made of vinyl chloride are placed on the lake bottom. The

chamber isolates a portion of the bottom sediment and its overlying water.

The overlying water wit'iin the chamber is mixed homogeneously by repeated

*, (4 times) withdrawal and injection of a part (ca. 50 ml) of overlying water

in the chamber using a syringe before sampling. In preliminary experiments,,

we confirmed that the overlying water within the chamber was mixed well by

this method. The overlying water was periodically sampled with a syringe

onboard, and then filtered with the same procedure as the laboratory sediment

core method.

Be:ause the volume of the overlying water within the chamber was far

greater than that of the water sampled for nutrient analysis, the second term

of Eq. (1 ;,as neglected. The cumulative amount of nutrient released f om

the lake sediment to the overlying water within the chamber at each sampling

was calculated by

r = V(Cn - Co) (2) A

where r = the cumulative amount of nutrient released from lake sediment

(/L 2); V volume of the overlying water of a chamber (L 3); Cn = NH 4-N con34 centration at n'th sampling in the overlying water (M/L38 Co initial NH -N

4

243
!3

concentration in the overlying water (MIL 3 and A - area of sediment-water

"interface in a chamber (L 2).

Mathematical Model Method

-- 2-

In estimating transport of dissolved species, such as CC , Na *, SO4 2

from sediments to overlying water, the Ficktan description of the transport

has been generally izcilized. In the Fickian description, the flux from sediment is directly proportional to concentration gradients of dissolved species.

A theoretical nu':rient, fLux was calculated from

R -- .DtD (3)

where R - nutrient flux (M/,2 /T)*; -prugity of the sAdiment (dimensionless); 1) t4a effective diffusion coefficient at t*C (1 2/T); and ,C/az the

gradient of nutrient concentration at qedlment-water interface (M/L ). We

cannot determine the accurate gradient of nutrient concentration at the

sediment-water interface experimently because the sediment-water interface

is very delicate and easily disturbed diiring sampling, Hence, the concentration gradient at the sediment-watpr inerfa•ce was estimated from the concentration gradient bezwven the overlying wat,-r and the interstitial, wat*r In the

uppermost sodiment layer (usually the top I or 2 cm of sediment)

'.C iC l over (3)'

whvr4, C in 6 NF1 4-N concentration of Interstitial water In the upper1IKst layer

of ,'edirnpnt (M/I.3); C - nutrient concentration in overlying water (M/I.);

over

and - the distancep from the bottom ;edimpnt surfaco to the central plane

of the uppermost sediment laJve- (L).

Many researcher% have attempted to evaluate the diffusion coefficient in

*edimrent u-%Ing varioust 70- 2 methods, 7.,8,18,•19bhut the- e.gtimate values ranged widely from

10 t 10() cmnee. ' The nutrient exchange of the sedimentwater tnterfae, Is a result of a combination of physical, chemical, and

hI' lea I prc eses such as molecular dlt ff.ion, hioturhation, physicalm

ml~i ',, and .4d-iorption-dosorption. These proce-tses are complex and dcldiffrIuit

to ,e-.tjrt' ur parately. Accsordiivlv, at present, it it difficult to evai;uatie

4fff-cTlivo dIffusion or trans;.'rt t-oefficlentes invorpu)ratin? the above-mentioned

f'lrnan nod cTan1l1•• .pplied the correlation of diffus•(on co'ef f icient

.ii .1 * ý)oro-,f t/ .. !,en by 'lanhelm 1 to the sell s*nt (if T'hite Lake and evilunated

flw< from thie sediment. l. er-anI had fnrmoul.it#e i relationship between

* T tie.

244
diffusion coefficients and porosity using -data from Manheirn. The value of

2.19 the diffusion coefficient D is approximately directly related to I*

D - DO(4)

where D is the value of the diffusion coefficient in the bulk (that is,

when =1). D0of ammonia is 9.8 x10 -6cm 2/see.

'9 Diffu~sion coefficients increase directly proportional to temperature

Dt - DCI + :it) (5)

where i - empirical constant (l/*C); and t m temperature (*C). The empirical

constant of ammonia is 0.04. In this study we calcuiLated diffusion coeffIcients from Eq. (3). Eq. (3)", Eq. (4), and Eq. (5).

Sampling of interstitial water in the uppermost sediment was conducted

as fol lowii. Sediment cores were taken with a coring device and immediately

transported to the laboratory. After the overlying water was removed carefujl l, minimizing disturbance of the sediment-wator interface, the sediment

core was se.ctioned into I- and 2-cm slices. These slices were inserted into

the rentrifulge-filter (Whatman (WC) tubes (shown in~ Figure 5) and centrifuged

at 3,000O rp'i. for 15 minutas with qRediment-water interface temperature, t2*1..

Tho filtraite wa-; analyzed for NH4-N with the same procedure as ovterlying water.

4

'erU~nt i-'-? coe .d t~e n-sit sedi!nt c re muetod, rain diather)-i hme

'~j'"'r WNsuol to n~i r' f tainles S~~-so metpe or h eemntn,

s FII-i ro tep .5. Th cnrifug~;~e feiter srifhem for i sapn Fgue 6R

Al t,*; o cpei m n ss~of e tho et- tevac aomi siniye amountisv of the- rlabortor

%ifri. t rtdI.en wee irety proporj sedmen torelamen9thoadmhe.isti hm
0 CJ

--4

b.j e. 4U),

V 00

z

tjao

404 IW4W apl" MPH ) ltO AItfn
S40

4.4

S20

S oo0

10

uA

0 20 40 60 80 100 hrs:

Time

Figure 8. Cumulative amounts of NH -N

4

release measured by the in-situ

chamber method, August 17-21

Eleven cores were taken in the maLhematicaL model method. Two sets of

surface sediment layers were separated from the cores sampled to estimate NH4-N

concentration of interstitial water in thr uppermost layet of the sediment,

i.e. 6 and 5 cores were used to obtain layers of 1 cm thickness from the sediment surface (0-1 cm, A2 = 0.5 cm) and those of 2 cm thickness (0-2 cm,

A?. = 1.0 cm), respectively. In this method t - 10*C of lake bottom temperature

and P = 0.95 measured from water content and density of sediment were used.

Table 2 shows the mean values, standard deviations, and coefficients of

variation of NH4-N flux evaluated from the labotatory core method, the in-situ

4

core method, the in-situ chamber method, and the mathematical model method.

The mean I'I -4N release rates evaluated from each rvethod ranged between 9.6 mg

9 4

N/m day and 16 mg N/m_ day. Similarly, the coefficients of variation

ranged from 15% to 39%.

Next, the precision of the N 4-N release rates determination among the

five methods (shown in Table 2), including two kinds of mathematical model

methods (' - 0.5 cm and .; - 1.0 cm), was compared. Table 3 shows the results

of statistical test on the differences of variances among the NH 4-N release

rates. No significant diffPrencP (P , 0.05) of the variances was found between

"1, = 0.5 cm and ' - 1.0 . rm in the mathematical model methods. There were no significant diffwrencrs among the two nmathematiraL model methods, the laboratory

247
Table 2. Mean values, standard deviations, and coefficients of variation

of NH -N flux evaluated from the laboratory core method, the

4 -

in-situ core method, the in-situ chamber method, and the mathematical model method

Methods Determined values

Mean SD %CV

(mg N/m2 /day)

Laboratory Core Method 11.5 1.76 15.3

In-situ Core Method 15.0 5.83 38.9

In-situ Chamber Method 9.6 1.55 16.1

Mathematical Model Method 15.7 3.04 19.4

(&Q = 0.5 cm)

Mathematical Model Method 13.2 2.94 22.2

= 1.0 cm)

Table 3. Results of statistical test on the differences of variances among

the NH -N release rates determined by the laboratory core method,

the in-situ core method, the in-situ chamber method, and the

mathematical model method (W = 0.5 cm and A23 = 1.0 cm)

Laboratory In-situ In-situ Model Model

Core Core Chamber (A2l 0.5 cm) (AJ2 = 1.0 cm)

Laboratory Core X NO NO NO

In-situ Core X NO NO

In-situ Chamber NO NO

Model (Al = 0.5 cm) NO

Model (&2 = 1.0 cm) _.

X = Significant difference (P < 0.05)

NO = No significant difference (P < 0.05)

248
core method, and the in-situ chamber method. Significant differenceŽ (P < 0.05)

existed between the in-situ core method and the laboratory core method, and

between the in-situ core method and the in-situ chamber method. Accordingly,

the in-situ core method reflected the least precision of the N114 -N release

rate determinations among the five methods as shown in Table 3. Results of

the statistical test indicated that there was no difference among the precision

of the NE4-N release rates evaluated from the laboratory core method, the

in-situ chamber method, and the mathematical model methods.

The differences of the mean values of NH4 -N release rates were examined

for the methods where no significant difference among the variances was found.

There was no significant difference (P < 0.05) between the mean values calculated from the mathematical model methods of AZ = 0.5 cm and AZ = 1.0 cm.

The mean values calculated from the mathematical model method of AZ = 0.5 cm

were significantly greater than those evaluated by the laboratory core method

and the in-situ chamber method.

However, the mean values calculated from the mathematical model method of

AZ = 1.0 cm were not significantly different from those evaluated from the

laboratory core method and the in-situ chamber method.

These statistical tests showed that the NH -N release rates calculated

4

from the mathematical model method of AZ = 1.0 cm did not differ from those

estimated by the methods of measuring the cumulative amounts of NH -N released

4

from sediment to overlying water. The mathematical model method, therefore,

would be substituted for the other methods that require long time incubation.

REFERENCES

1) Hosomi, M., Okada, M., and Sudo, R.: Release of phosphorus from sediments.

Verh. Internat. Verein. Limnol. 21, 628-633 (1981).

2) Hosomi, M., and Sudo, R.: Studies on the effects of sediments on algal

growth--Algal growthi potential of sediments. Research Report from the

National Institute for Environmental Studies No. 6, 115-121 (1979).

3) Okada, M., and Sudo, R.: The effects of sediment on lake eutrophication:

the application of algal assay procedure. 4th U.S./Japan Experts Meeting

on Management of Bottom Sediments Containing Toxic Substances. EPA-600/3-

78-084. Environmental Protection Agency, Corvallis, OR.

4) Larsen, D. P., Sickle, J. Van, Malueg, K. W., and Smith, P. D.: The effect

of wastewater phosphorus removal on Shagawa Lake, Minnesota--phosphorus

supplies, lake phosphorus and chlorophyll a. Water Research, 13, 1259-

1272 (1979).

5) Welch, E. B.: Nutrient diversion--resulting lake trophic state and

phosphorus dynamics. EPA-600/3-77-003, Environmental Protection Agency,

Corvailis, OR.

249
6) Holdren, G. C., Jr., and Armstrong, D. E.: Factors affecting phosphorus

release from intact lake sediment cores. Environmental Scienc & Technology,

14, 79-87 (1980).

7) Freedman, P. L., and Canale, R. P.: Nutrient release from anae robic sediments. J. Environ. Eng. Div., ASCE, 103, 233-244 (1977).

8) Nishimura, H., and Nakajima, M.: Nutrients exchange between sediment-water.

Research Reports of the Environmental Science, BIO-RIO-I, 51-7 (1978).

9) Sonzogni, W. C., Larsen, D. P., Malueg, K. W., and Schuldt, M. D.: Use of'

large submerged chambers to measure sediment-water interaction . Water

Research, 11, 461-464 (1977).

0

10) Schippel, F. A., Bagander, L. E., and Hallberg, R. 0.: An ap atus for

subaquatic in-situ measurements of sediment dynamics. Stockholm Contributions in Geology, 24, 103-108 (1973). a

11) Hallberg, R. 0., Bagander, L. E., and Engvall, A. C.: Dynamics of

phosphorus, sulfur and nitrogen at the sediment-water interface. Environmental Biogeochemistry, 1, Ann Arbor Science, 295-308 (1976).

12) Chiaro, P. S., and Burke, D. A.: Sediment oxygen demand and nutrient

release. J. Environ. Eng. Div., ASCE, 106, 177-195 (1980).

13) Hargrave, B. T., and Connolly, G. F.: A device to collect supernatant

water for measurement of the flux of dissolved compounds across' sediment

surfaces. Limnol. and Oceanogr. 23: 1005-1010 (1978).

14) Kamiyama, K. Okuda, S., and Kawai, A.: Distribution of NH -N i lake

sediments and NH4-N release from sediments. Water and Waste, 2ý1, 29-35

(1979).

15) Tochigi Prefectural Government: Report of the effects of lake sediment

dredging on the water quality in Lake Yunoko. Tochigi Prefectural Association of Pollution Controls and Managements (1978).

16) Fujimatsu, M.: The impact of advanced wastewater treatment andl ban of

phosphorus detergents on the water quality in Lake Yunoko. Tochigi

Prefectural Association of Pollution Controls and Managements (1981).

17)' U.S. Environmental Protection Agency: Methods for chemical analysis of

water and waste. EPA-625-/6-74-003a, 168-174 k1976).

18) Manheim, F. T.: The diffusion of ions in unconsolidated sediments, Earth

and PLanetary Science Letters, 9, 307-309 (1970).

19) Lerman, L.: Geochemical processes water and sediment environments.

John Wiley & Sons, p. 481 (1978).

230

2•O •
DPEDGING AND MANAGEMENT PROBLEMS IN LAKE SUWA

K. Nikaido

Chief Engineer

Japan "Bottom Sediment Management Association

M. Akabane

Director of Suwa Constructic'n Work Office

Nagano Prefecture G)vernment

ABSTRACT

Dredging in Lake Suwa commenced in 1969 and is still

in progress. The start of this dredging work was very

early in the history of environmental improvement in our

country. The first stage work, which aimed to re,.ove

sediment from shallow zones below 2.5 m, was finished in

1980. However, it brought about no remarkable improvement

in water quality. These results were not surprising since

the dredged area was only a small part of the lake.

In review of the results, a new project was established in 1981 to dredge the remaining deeper zones. The

project began this year. This paper deals with the dredging and management problems of this new project.

BACKGROUND C

Lake Suwa, located in Nagano Prefecture in the central part of Japan, is

the 15th largest lake in our country and is 759 m above sea level.

2 2

It has a basin of 531.2 km ,a lake area of 13.3 km , and a mean depth of

4.7 m. The lake is surrounded by urban areas including several cities such as

Okaya, Suwa, Shimosuwa, and Chino. The total population is about 150,000. As

this area is a famous hot spring zone, it has a large number of tourists in

addition to the residents. It was natural that urban drainage would flow into

the lake and cause serious pollution problems.

The COD concentrations in the lake water changed with time as shown in,

Figure 1. They increased gradually from 1960, and reached a maximum value of

10 ppm in 1973 and after that held constant between 6 ppm and 10 ppm.

The lake is designated as an A type body of water by the Environmental

Agency, in which COD concentrations must be maintained below 3 ppm. The present state is over twice that. Lake pollution advanced so seriously that the --

lake suffers from a large crop of algal blooms in summer.

251
I0

8

ca°

6

4

2"

9M6 1960 1965 1970 1975 190.

Figure 1. Variance of COD concentrations

SEDIMENT POLLUTION

In 1978 a sediment survey was conducted on a large scale as shown in

Figure 2. Sediment samples were taken from 48 points.

The average nutrient concentrazions in sediment surfaces were as follows:

T-P 4100 mg/kg

T-N 4920 mg/kg

.b.2

4 --3 227 17 I"N

S41 35 30 ,,, 116 12 15 i

46 o L36 29 24 15 13 1 4 ..

39 3 7 2 Z 25.!

0 5 1o=, km

Fig-ure '2. Sediment samplingc conduct-ed in 1978
/ /

/

j-.4

Their maximum values were extremely high, indicating a large deviation as

follows:

Max T-P = 35,000 mg/kg

Max T-N = 7,950 mg/kg

From these data, it was found that large quantities of nutrient material

have accumulated on the lake bottom. It is likely that the release rates from

sediment might also be great. This is demonstrated by release tests, 2 which

show that the release rates were 11.9 kg/m 2 /day for T-P and 15.6 mg/m /day

for T-N. These release materials generate a large peak in nutrient concentrations in summer, as Yoshida pointed out, and result in a large crop of

microcystes.

DREDGING PROJECT ""

I

The dredging in Lake Suwa commenced in 1969 and is still in progress.

The first stage of the dredging work removed sediment from shallow areas below

2.5 m (Figure 3). Completed in 1980, the total amount of dredged material

equaled about 1,500,000 m3 .

This dredging had no significant effects for the following reasons: C

a. The dredged area occupied only about 15% of the total area.

b. The majority of the polluting sediment is in the deeper zones, as

Figure 4 shows.

I

C. The dredging rate was too small.. It required 12 years to remove

sediment that occupied only 15% of the whole area.

Considering these results, it was decided to dredge the deeper depths as the second stage work. Beginning in 1981, the total amount of sediment to be

dredged was estimated at about 5,300,000 m . In view of the results up to I

now, the following, conclusions are drawn:

I

Figuire 3. Dredged area in the first stage work

253
D. ISTANCE OFFSH4ORE / i 0 z,..

wo

uj

2000

3000 Iz

400 z

0 5 O 1 - 5000 = •

MG/KG

Figure 4. Sediment pollution

versus distance offshore

(a) The dredging should commence in the heavily polluted areal. The

area to dredged is divided into four blocks (Figure 5). The average

nutrient concentration in sediment for each block is as follows:

No. 1 No. 2 No. 3 No. 4

T-P mg/kg .7206 3225 3528 2439

T-N mg/kg 5611 4989 5402 3456 -

From this it can be seen that the 1st block is the heaviest in

pollution and the 4th is the lightest. Consequently, the dredging

sequence will be I ÷ II - III I IV.

M6

%-i°

Figure 5. Four blocks of dredge area

254

0.,

o.N.
I

(b) The work period will be 20 years. Although the shortest possible

period is desirable, when considering the financial difficulty,

20 years is judged appropriate.! The dredging rate of the second

stage is much larger than that of the first stage.

The removal thickness of sediment was determined from the following:

(1) Vertical distribution of nutrient concentrations in

sediment against sediment depth.

(2) Reduction of release ratesl by sediment removal. 0

(3) Reduction of sediment oxygen demand by sediment removal.

The relationships between release rates and removal thickness are

shown in Figure 6. The lower the release rate, the thicker the

removal thickness. However, the increment becomes smaller according 0

to the removal thickness; the release rates decrease no further if

the thickness is over 50 cm. From this, the removal thickness was

set at 50 cm.

K MGflJ2,V S0

2 MG/M /DAV Z

0. 120

0¶

- 10 S

1 20 3 4,o 0 '

REMOVE THICKNESS. CU REMOVE THICKNESS. CM

Figure 6. Relationship between release rates and removal thickness

MANAGEMENT OF DREDGED MATERIAL

In the second stage work, the most difficult problem is management of the

dredged material. In the first stage work, the dredged material was used

mostly for road banking (built around the lake at the similar time). Such a

use is not feasible at this time since road building is nearly complete.

At Lake Suwa there is no space for disposing the dredged material due to

the narrowness of the land surrounded by high mountains. Therefore, the

dredged material has to be transported to other places, where it might be used - .

for banking and other purposes. To do this, it is necessary to dewater the

dredged material as quickly as possible at the lake side.

The dewatering methods may be cla3sified in two ways: mechanical dehy- ,

dration and in-pond sedimentation. To examine these two methods from the

technical and economical view points, tests on mechanical dehydration were

255

. .. .- . . ..--- . .
conducted in 1981, and tests on dewatering by in-pond sedimentation were

scheduled for 1982.

Mechanical Dehydration Tests In Situ .0

The dredged material was removed 2 by a dredge with a 420 h.p. pump and

transported hydraulically to a 7000-mr disposal pond (Figure 7).

The test was performed near the disposal pond. To promote sedimentation

in the management pond, 45 ppm of inorganic flocculant (PAC) and 3-7 ppm of

polymeri. coagulant were added to the pipe at the pond entrance (Figure 8).

A filter press was chosen to dewater the dredged material. The filter press

has 30 chambers having an area of 0.9 m and a width of 117 cm. The flowchart

of the test plant is shown in Figure 9. The layout of the dehydration test

plant is indicated in Figure 10.

The tests were carried out in such a way that: :

a. The densified slurry was pumped up from the management pond by a submerged sand pump and fed to the storage tank (27 m3 ) and therein

mixed uniformly by a sand pump with a mixer.

0• 0

Dredged Area %

Dredge '-- \\ ,

Disposal

Figure 7. Disposal and test site

b. The homogeneous slurry was transported to the agent :,.ixing tank

(1.5 m3 ). Gravel or wood chips were removed by a screen at the inlet

to the tank.

c. A predetermined amount of flocculant was added to the slurry in the

tank and agitated with an agitating vane, and was then transported to

the slurry tank (6 m3 ) set at the bottom.

236

256 "-..S
Figure 8. Management pond and test site

I0

I K

'0 I F SAN UM

2 0 AE'APNK

'2 N PA SA N Pj'N IVT *AGIT

6 IANX

'2 3L~MRG~L uMPp

fiR7 F' . Fl'cptofts *p.Ifu

9 C3F T , )V2yn
I

SUBMERGED

PUMP

i .

pUSMERGEO OEHMYRATED CAKE

PUMP

FILTER

S j BELT COONVEYOR

S].LURRY PUJMP

AGENT GENERATOR MI XING

TANK

) 0 TANK

MIXER

MANAGEMENT POND0 SAND PUMP

i•:,lr . 1). L.i'',llt ,f test pl.1nt

". 5'8
d. The coagulated slurry was drawn out from the tank bottom by a high

pressure slurry pump, pressed into the filter press under pressure,

and dehydrated at a pressure of 3-5 kg/cm2 . After the predetermined

quantity of slurry was fed, the filter frame was opened and a dehydrated cake discharged.

"e. The turbid filtrate which came out at the first stage of the dehydration process was returned to the settling pond. Ihe clarified filtrate was stored in the neutralizing tank (22 m') and then discharged

into the lake.

The test conditions were set as follows:

a. The specific gravity of the slurry pumped up from the management pond

was adjusted to a range between 1.04-1.08.

b. Three kinds of flocculant were used: slaked lime, alum, and cement.

Ihe use of alum was expected to neutralize the dehydrated 3cake with

the mixture of slaked lime. Their dosage was 1.0-10 kg/m of slurry.

c. The feeding duration of slurry to the press was 20-135 min.

I'est Results

!),h'.drrited Cake

1he prop,-rtita of the d.-hydrated cake are shown in fable 1.

Table 1. Cake Properties

Slaked lime

I em Unit Slaked Lime and Alum

"ý'itcr ctntecnt 135-166 110-166

nit weigIt g/cm 1. 30-1. 34 1.28-1. 32

10.0-10.7 8.4-9.2

(CO) m./ 30. i-48.6 39.,4-44 .7

4 4' . 6-5. 5 4.1-5.3

m4/g 2.1-2.2 2.0-2.2

I:,-n : 1/ . 2-2.9 1. 8-4.0

mg/k 4 3.8-5.02.2-,. 3

Ihe di "ertnc b• '-t'n single (slaked lime) and mixed coaculants (staked

li me Ind 1, In ) a1:,..rtd in the ; p)H values, with the latter indicating the lower

239
Filtrate

The properties of filtrates are shown in Table 2.

r' Table 2. Filtrate Properties

Only Slaked Lime and

Iten ____ Unit Slaked Lime Alum Mixed

pH 10.4-11.4 7.6-9.4

"SS mgi, 14.0-17.4 6.0-17.0

iurbidity degr. 5-9 1-8

COD mg/, 19.3-22.7 6.4-12.5

I'-N, mg/, 5.0-7.0 2.6-3.5

g 1-P mg/,. 0.25-0.30 0.06-0.15

rhe use of mixed coagulants ve good results for every item and is

recormnended over slaked line.

Relationship Between Filtration Rates a,,d Coagulant Dosaga

lhe filtration capacity is normally repr- nied in terms of filtration

rate, which denotevs the quantities of the dehydrated cake per unit of filtration area and mnit time. From the test resilt'i, it 'q found that the filtration rates depend upon the -:pecific _,ravit. of the slurry, kinds of coagulant,

and water content o thev cake. lile tfsr results are summarized in Figure ii.

, Fi ure ii silows, the hi.•her the coagulant dosage, t... higher the filtration rate. However, tihe filtration rate stops increasing beyond a certain

potiit.

Fr,•m these data, we can say that an appropriate filtration capacity for

lake sediment in Suwa i- 4.75 k4'm-/hr of Jredged sediment3.

C INC IU I" NS

I' te:;t:t rcs :ltI ; ire - irar izwd ill lil;le 3.

,ICu te~t •ve ,uri I e:d t ne I:): li cal!t : -eliianical dehvdr~ition to sedi-

•,t[ d." iterlo:•,, i. ",•t idvint,:eos 'ointM of the mechanical d,,hydrator

rt: (I) m'ii::'aI wltvr 0!',.•it ,} t' ' cak,, 12) mini:rial tra!tment time, , 'd

,Ci::t :.I. t} t:t"c :Iditi,:i- iL it '4,iwa .ike since tht17t: is :'o ',ICC

-)r J.i ; 1. ':re-v*" , ii.t t Ltt the , l. i tho ,

~ A.i ii~ ;v.r~itcr- :'a. toeL Ili JI co-t 11 petIt ion and eqi pýIuiti~et. (I

.LIIy t Ii p ro:1,:72 , test-i on1 dwatri hy i: -!-11nd j -edi.imntat i, ire ,* sced:hled

•: , i:•c td il 1'148 . Ihe technical anud economical compari son iet,, :ien t 'em w i].e. c:•L.iI.' l:il• upllonl te-t comnjiet, Ion.

-I)
Wacer

12 Sedimeu. G.ntent

Sp. Craviry of Cakes

OIL U7- G L08 W 150

S-- w .135

p/~ -- &L34 --- w,3

0 .0 . 150 Cz

DOSAGE OF COAGULANTS. KG/TON OF DREDGED SEDIMENTS

Figure li. Relationship between filtration rates and dosage of coagulants

Table 3. Results of Mechanical Dehydration Tests

D)o'..a•e ot

Coa:<ulant s per

tan of )redged

_ !J•rcd-',yd .Mlnrr.'".... Sud irncnts Dehydrated Cake Filtrate

'1l) DXnsit. (1) Slaked line (1) Water content (1) pH 7-8.b

2(2 55 56 mh/;

et

. 4 , .,32) 1--- tu

533

"-(o0L ;hH) t/o r

tir .hPtim

V m/m

% ", - . ,
EMERGENCY RESPONSE EQUIPMENT TO CLEAN UP HAZARDOUS CHEMICAL

RELEASES AT SPILLS AND UNCONTROLLED WASTE SITES

I. Wilder

Chief, Oil and Hazardous Materials Spills Branch

Solid and Hazardous Waste Research Division

Municipal Environmental Research Laboratory

U.S. Environmental Protection Agency

Edison, New Jersey 08837

ABSTRACT

This paper reviews some of the research activities

of the U.S. Environmental Protection Agency (EPA) regarding the development of emergency response equipment

to control hazardous chemical releases. Several devices

and systems have been developed by EPA for environmental emergencies involving spills and uncontrolled waste

sites. Many of these have already been made available.

commercially by industry, including a mobile physical/

chemical treatment system for processing contaminated

water at hazardous incidents and a mobile laboratory

for onsite chemical analyses. Other operationally

ready devices addressed in this paper s.clude: a mobile

stream diversion system for isolating se.;.,ents of small

streams to facilitate the remove" t c-rntiaminated sediments; a-portable back-pack pi .. h-Arte foam diking

system for the containment of ;pilIle rne, icals; and an

acoustic emission-based spill alert devK_ for detecting imminent dike failure at lagoons containi,-j toxic

and hazardous wastes. Prototypical Eguipment, described

in this paper, which are now undergoing shakedown testing andevaluation include: a mobile soils washing 7

system for extracting spilled materials from excavated

soils onsite; and a mobile, field-use incineration

system for the thermal destruction of toxic organic

compounds.

INTRODUCTION

Problem

Billions of metric tons of oils and hazardous chemicals are produced and

handled annually in the United States. These materials range from gasoline

and fuel oils, to vegetable oils, sulfuric acid, lye, chlorine and chlorinated compounds, cyanides and isocyanates, and include hundreds of millions of

kilograms of toxic pesticides and pharmaceuticals. Millions ot metric tons

262
are released into the water, land, and air environment each year--often with

catastrophic consequences--due to spills resulting from ship, truck, and train

accidents, equipment malfunction, transfer line failure, broken pipelines,

lagoon dike rupture, overfilling, leaking storage tanks, container puncture,

flood, earthquake, fire, and explosion.

Similarly, millions of metric tons of hazardous wastes are generated in

this country each year from manufacturing, processing, and other industrial

operations. Disposal of this substantive quantity of waste is a matter of

great public concern in the wake of numerous case histories involving negligent dumping practices resulting in several instances of contamination that

have severely damaged the environment and threatened human life. Perhaps the

most dramatic example of inadequate disposal of hazardous chemical wastes

occurred near Niagara Falls, New York, where hundreds of families living

along an abandoned waste disposal site, known as Love Canal, had to permanently evacuate their homes when the toxic chemicals migrated from the site

and seeped througn the ground into their basements.,

'Legislative Background

The U.S. Congress addressed the problem of oil and hazardous material

spills in Public Law 95-217, the Clean Water Act (CWA) of 1977, and its predecessor statute, Public Law 92-500, the Water Quality Improvement Act of

1972, which authorizes the Federal Government to take emergency response'

action when oils and specially designated hazardous substances are discharged into navigable waters (1). These statutes, however, are seriously

limited in their authority to deal with the variety of problems caused by

releases of hazardous substances onto land or into groundwater and air.

Public Law 94-580, the Resource Conservation and Recovery Act (RCRA) of

1976,,was the first comprehensive Federal legislation to deal with the hazardous waste issue. RCRA establishes a regulatory system to track hazardous

wastes from the time of generation to disposal. It requires safe and secure

procedures to be used in treating, storing, and disposing of hazardous wastes

and is designed to prevent the creation of new Love Canals in the future. -

RCRA, however, does not permit the government to respond directly to the

proolems caused by improper (uncontrolled) hazardous waste disposal sites

already in existence.

Legal authority to overcome the limitations of both CWA and RCRA was

provided in 1980 by the enactment of Public Law 96-510, the Comprehensive

Environmental Response, Compensation, and Liability Act (commonly known as

Superfund) (2) which authorizes Federal emergency response to any hazardous

substance release into the environment which endangers public health and

welfare--including the cleanup of uncontrolled hazardous waste sites and the

mitigation of spills not only in navigable waters, but also in groundwaters,

soils, sediments, and the atmosphere.

RESEARCH AND DEVELOPMENT

Successful implementation of the Superfund legislation, as well as the

Clean Wdter Act and the Resource Conservation and Recovery Act, requires major

263
research and development efforts. Controllinq and cleaning up hazardous substances is a relatively complex field. Specialized equipment and techniques

are needed in order to respond quickly and effectively to emergencies and to

dispose of the materials in an environmentally safe manner. Both industry

and the government are working diligently to learn mare about controlling

these materials and to develop appropriate cleanup devices and equipment.

Within the U.S. Environmental Protection Agency (EPA), the Municipal Environmental Research Laboratory (MERL) has the lead role for research and development related to hazardous waste environmental emergencies. Through a program

at its Oil and Hazardous Materials Spills Branch in Edison, New Jersey, MERL

is developing prototypical equipment and experimental techniques for the

prevention, control, and abatement of multi-media pollution from hazardous

chemical spills and mismanagea hazardous waste disposal sites.

The main thrust of the program centers around emergency response research

to develop the tools to remove the immediate threat of a hazardous material

1 "V

.4r%

Figure . Oil and Hazardous Materials Simulated Environmental Test Tank

(HMSETT), the world's largest facility for the environmentally safe testing of spill cleanup methods and technologies.

264
incident in order to control the emergency and protect human health and the

environment. A major testing facility of the program is the Oil and Hazardous Materials Simulated Environmental Test Tank (OHMSETT), which consists

chiefly of a 9.8 million liter (2.6 million gallon) concrete tank with mobile

bridges, a wave generator, and a simulated beach (Figure 1). OHMSETT is the

only facility in the world of its kind for the testing, evaluation, and development of full-scale spill cleanup equipment, devices, and systems under

controlled, environmentally safe and reproducible conditions (3,4).

Development of hardware and techniques is carried out from the conc,.c.!:

stage through the prototype stage to field testing and demonstratior. A

major objective of the program is to demonstrate the applicability 5T the

prototypical equipment at spills and waste sites throughout the rountry,

thereby stimulating the commercial adoption or adaptation of the devices and

encouraging private firms to manufacture or use similar equipment.

Equipment or Sstems Currently Field Ready

Several prototypical emergency response devices have been developed,

tested, evaluated, and demonstrated to the point where they are fully operational (5). Examples of some of these field-ready devices follow:

Mobile Physical/Chemical Treatment System

This device (Figure 2) is designed to remove hazardous chemicals from

water by a variety of physical/chemical treatment steps employed in the

4 ..

Figure 2. Mobile physical/chemical treatment system for processing contaminated water.

265
field. It contains equipment for coagulating and settling suspended solids,

filtering very fine particulates, and adsorbing dissolved organic contaminents usinq granular activated carbon. Mounted on a 13.7-m (45-ft) drop deck

trailer, the system (6) incorporates three mixed-media filters, three pressure

carbon columns (which may be used in parallel or in series), pumps, piping

controls, and a 1O0-KW diesel generator. A support trailer is equipped with

additional pumps and several collapsible rubber tanks which serve as sedimentation, chemical reaction, and storage containers. Contaminated water can be

processed at flow rates between 379 and 2270 liters (100 to 600 qallons) per

minute. The system has been used at more than 30 cleanups of uncontrolled

hazardous waste sites and spills of hazardous materials around the country. 7

Commercial units patterned after the EPA system are now routinely, employed.

Mobile Decontamination Station

This 12.2-m (40-ft) trailer (Figure 3) is engineered to provide onsite

safety support for emergency response personnel. It is intended to ensure

that exposed personnel do not leave the site without a proper washdown and

clothing change. The unit is placed at the boundary of a cleanup site, and all

personnel are required to pass through it when entering and leaving the site.

The trailer is divided into three compartments: [1] a "clean" room with

lockers for storing street clothing; [2] a shower room; and [3] a "contaminated" room witn lockers for work clothing. This room also includes a clothes ... washer and dryer. The decontamination station is equipped with a freshwater

supply and holding tanks for wastewater which must be processed prior to discharge. The unit has alreaay been used in the field in support of cleanup

activities, and has been duplicated by a commercial spill cleanup contractor.

Fiyure 3. MooiIe decontamination station for use of field personnel at

cleanup activities involving toxic materials.

266

S ,,.. 4
/

Mobile Laboratory

This unit, contained within a 10.7-m (35-ft) semi-trailer (Figure 4), is

designed to provide analytical services during the cleanup of hazardous materials at spills and uncontrolled waste sites (7). Having analytical capabilities at the field site avoids delays inherent in shipping samples to a central

laboratory. The mobile laboratory contains a broad range of sophisticated

instrumentation, including a gas chromatograph/mass spectrometer (GC/MS), computerized gas chromatographs, an atomic absorption spectrometer, infrared and

fluorescence spectrometers, and other highly sensitive analytical tools.

Special sample processing techniques and glove boxes permit safe handling of -. high concentrations of toxic-chemicals. During the past few years, the

mobile laboratory has been used to perform several thousand sample analyses

in a variety of emergency response situations. The laboratory has been used

as a model by a number of spill cleanup contrdctors who have built similar

mobile units for commercial application.

4

* 4

/4

4

7 I'

Figure 4. Mobile laboratory to provide analytical services at emergency

incidents involving hazardous chemicals.

Acoustic Emission Monitoring Device

This device (Figure 5) is designed to provide an early warning of potential failure to earthen dams containing hazardous materials (8). Earthen dam

ponds can be found at almost any hazardous waste site in the United States.

Many of these impoundments are unstable and, with slight overstressinq (such

as from neavy rains), may collapse and spill their contents into the environment with potentially drastic consequences. The acoustic emission monitoring

device detects instability in earthen dikes by measuring noises generated by

soil particle movement. The intensity and frequency of these sounds (acoustic emissions) have been correlated with stress levels for various soils and,

267
.1 I

therefore, can be used to indicate stability of dike structures. Acoustic

emissions are transmitted to the surface of the dike through metal rods (waveguides) inserted into the impoundment wall. These sounds are converted to

electrical signals which are amplified and recorded for analyses. The device,

wnicn has been commercialized in at least three versions, has received wide -I

recognition as a simple, portable, inexpensive tool for assessing impoundment

stability and preventing spills.

II

I ' "

Figure 5. Acoustic emission monitoring device for detecting imminent

dike failure at lagoons containing toxic and hazardous wastes.

Foam Dike System

This system (Figure 6) is designed to provide a rapid response method for

containing or diverting the flow of many spilled hazardous chemicals (9,10).

The diking unit consists of an 18-kg. (40-1b) back-pack device that generates

approximately 0.8 m3 (30 ft 3 ) of two-component, very rapid set-up polyurethane foam. Larger sized commercially available units are capable of delivering 1.8 m3 (65 ft 3 ) of foam which provides sufficient material to construct

a DarriFr 0.3 .n (1 ft) high by 0.3 m (I ft) wide by 6 m (20 ft) in diameter,

268

/1
.1

whicn could impound approximately 7570 liters (2000 gallons) of spilled hazardous liquid. The polyurethane foam adheres well to most dry surfaces (pavement,

earth, etc.) for making stable dikes, and can also be used to plug storm drains

on streets to prevent spilled hazardous materials from entering sewer systems.

The diking unit has been designed as a compact, portable device to be carried

by individual operators such as truck drivers or railroad train personnel.

Several fire departments in this country have already used the foam diking

system in emergency response operations involving hazardous substance releases.

Figure 6. Foam dike system for the emergency containment of spilled . hazardous chemical s. T•• ,~,..

Mobile Stream Diversion System

The system (Figure 7) is intended to isolate segments of small streams so

that contaminated sediments can be removed easily with mechanical earthmoving

equipment (11). This approach is an alternative to dredging which typically

requires extensive water treatment to remove contaminants that become suspended or dissolved during the pumping operation. Dredging also often leads

to the downstream spread of the contaminant as a result of resuspension of

bottom muds and silts. Isolation of a contaminated stream is accomplished by

damming the stream above the impacted area and bypassing the normal stream

flow. The stream diversion technique permits the spill-impacted segment to

dry, thus facilitating mechanical cleanup. The major components of the system are booster pumps, submersible pumps, generators, a crane, and aluminum

irrigation pipe. The system is designed to bypass the flow (up to 0.37 m3 /s

[13 ft 3/s]) of a small stream for distances up to 914 m (3000 ft). An

alternative use of the mobile stream diversion system is to divert or reroute

surface runoff water around a highly contaminated hazardous waste site and

prevent the spread of contamination to areas down gradient of the site.

269

p. .. .V•...
*.

2-0•

Figure 7. Mobile stream diversion system for isolating segments of small

streams to facilitate the removal of contaminated sediments. O

Hazardous Materials Spill Warning System

This in-stream system (12), wnich i's capable of detecting a variety of

spilled hazardous materials in waterways, is housed in an air-conditioned

0

Figure 8. Hazardous materials spill warning system for the continuous;

in-stream detection of a broad variety of spilled hazardous

chemicals in water.

270

~.
* 8.2-m (27-ft) automotive trailer (Figure 8). The system operates continuously at an unattended station, without maintenance, for a period of 14

days. A submersible pump in the watercourse supplies uninterrupted water

samples to instrument consoles in the trailer. The consoles contain the following: [1] pH, electrical conductivity, and oxidation-reduction potential

sensors for the detection of acids and bases, ionic compounds, and oxidizing

and reducing substances, respectively; '2] a total organic carbon analyzer

with a built-in recorder for the detectcn of organic compounds; [3] a differential ultraviolet absorptimeter for the detection of aromatic compounds;

and [4] a control console with strip chart recorders. The hazardous materials

spill warning system has already been demonstrated in the field to monitor

discharges from uncontrolled hazardous waste sites.

Equipment or Systems Currently Under Test and -valuation

A number of prototypical emergency response system! are now undergoing

final shakedown testing and evaluation prior to full-scale field trials.

Examples of some of these systems follow:

Mooile Incineration System

This system (13) was developed for field use to destroy hazardous organic

substances collected from cleanup operations at spills and uncontrolled haz-

* ardous wdste sites. The unit is designed to EPA's PCB destruction specifications (under Puolic Law 94-469, the Toxic Substances Control Act of 1976) to

provide state-of-the-art thermal oetoxification of long-lived, refractory

organic compounds. Hazardous substances that can be incinerated, for example, include compounds containing chlorine and phosphorus (such as PCS's,

kepone, dioxins, and organopnosphate pesticides) which may be in pure form,

in solution, in sludges, or in soils.

The mobile incinerator consists ot four over-the-road trailers (Figure 9 j

with specialized combustion equipment, air pollution control devices, and

monitoring instrumentation. Organic wastes are fully vaporized and completely or partially oxidized at 9820 C (1800 0 F) in a refractory-lined

rotary kiln. Off-gases are passed through a secondary combustion chamber at

1204 0 C (2200 0 F) where thermal decomposition of the contaminants is completed. Acid gases and particulates generated by the combustion process are

removed in the system's sophisticated air pollution control apparatus. A

comprehensive monitoring system is used to analyze the flue and stack gases

for cumoustion and emission components and is designed to automatically halt

the feeding of wa;te to the incinerator if gas emissions exceed acceptable

levels. Design processing rates for the incinerator are 4080 kg/hr (9000

lb/hr) of contaminated dry sand, or 680 kg/hr (1500 ib/hr) of contaminated

water, or 284 I/nr (7D gal/hr) of contaminated fuel oil.

A series of test burns with fuel oil has already been completed. In

order to systematically evaluate the equipment, PCB trial burns are currently

undpr way. The',e trials arp intended to demonstrate the incinerator's ability

to meet or exceed the performance requirements established by Federal, State,

and municipal regulations. After the trials, the system will be demonstrated

dt several hazardous waste sites arourd the country.

271
°An

Figure 9.' Mobile incineration system for the onsite destruction of

refractory organic compounds.

Mobile Carbon Regeneration System

Waters contaiinateo with hazardous substances can now be cleaned with

water purification equipment such as the EPA mobile physical/chemical treatment system (discussed above). Systems of this nature, which utilize granular activated carbon to adsorb the organic contaminants from the water, can

be. maae more cost-effective with onsite regeneration of the spent caroon--

thereby eliminating the problems associated with the transportation of contaminated carbon to a secure landfill or an offsite regeneration facility.

The mobile carbon regeneration system (Figure 10) provides a safe and

effective method for detoxifying/regeneratipy contaminated carbon at the

cleanup site. The system (14), mounted on : 13.7-m (45-ft) semi-trailer, contains a rotary kiln that heats the carbon in a slightly reducing atmosphere

to about 9820 C (1800 0 F) and releases the adsorbeo contaminants as a vapor.

(The atmosphere in the kiln is conditioned with water to enhance reactivation

of the carbon.) The vapor passes into a secondary combustion chamber where

it is totally deccmposed. The flue gases are quenched with water sprays and

scrubbec 4itn alkaline solution to neutralize acids and remove particulates

before venting to the atmosphere. Once the carbon is cooled with water, it

is reauy for reuse. The design processing rate for the cdrbon regenerator is

45.4 kg/hr (100 lb/nr) of dry granular activated carbon with 90% of the

carbon's adsorption capacity restored after regeneration.

272
The mobile carbon regeneration system is now undergoing comprehensive

shaKeoown testing and evaluation, and is expected to be ready for field

demonstration during 1983.

414Z

Figure IU. Mooile carbon regen~eration system for field use in

reactivating spent granular activated carbon used in

spill or waste site cleanup operations.

Mobile Soils Washing System

This system (currently under development) is being designed for onsitp

removal ot a oroad range of hazardous materials from excavated soils (15).

The soils washer is expected to oe an economical alternative to the current

practice )f hauling contaminated soils offsite to a landfill, and replacing

tne excavated volume with fresh soil onsitp. The system will be capable of

extracting contaminants from soils--"artificially leaching" the soil using a

water-based cleaning agent--and thereby enabling operators to leave the

treated soil onsite. To accomplish this, the soil is passed through a rotating drum screen water knife soil scrubber wnere soil lumps are broken apart

by intense jets of water, and chemicals are stripped from soil particles.

The resulting soil slurry is fed into a 4-stage counter-current chemical

extractor (-imilar to Figure 11). Each stage consists of a mixing, frothflotation cell connected in series with hydrocyclones which centrifugally

separate solids from liquids. The soil particles are agitated repeatedly in

washing fluid and are progressively ' :ontaminated as they flow through each

stage. The cleansed soil is tnen -eturned to the site. The extracted hazardous contaminants are separated prom the washing fluid using physical/chemical

treatment procedures (flocculation, sedimentation, carbon adsorption, etc.).

The cleaned washing fluid 1o recirculated while the separated and concentrated

contaminants are dispose. of by appropriate means.

273
0

The prototype soils washing system will be capable of processing 3 to

"14 m3 (4 to 18 yU3 ) of contaminated soil per hour, depending on the soil

particle size and the nature of the contaminant.' The device is expected to

be ready for shakedown testing and field trials in 1983.

i

U

Figure 1). Chemical extractor for separating spilled materials from

excavdted soils onsite.

Moolle In Situ Soils Treatment System

inere large volunes of suosurface soils are contaminated at spills or hazarious waste sites, excavation of the soil is not economically feasible. A

)urIfercidl.ly dvailaole alternative approach is to flush the soil in place

oitn water. The mobile in situ soils treatmernt system (16) offers an innovative, improved technique for treating contaminated subsurface soils in place

at redouced costs, in torms of dollars per kilogram of contaminant removed.

The teLhnique employs water flushing with additives, and detoxification by

chemical reaction.

The system (Figure I1) is mounted on a 13.1-m (43-it) drop deck trailer

and consists mainly of mixing, piping, and pumping equipment. In situ containment can oe accomplished with this system through direct injection of

grouting material into the soil around the contaminated area, thereby isolating the ared. The contaminants are then treated in place by water-flushing

with additives or by other methods such as oxidation/reduction, neutralization, or precipiLation. Specia,ý/ prepared solutions of wash water can be

delivered into highly contaminated soil through 16 injectors (slotted or perforadted pipes which are inserted into d series of holes drilled into the

i:npacted area). A vacuum well point withdrawal system creates an artificial

hydraulic gradient which draws the wash solution from the injectors through

2

274

p
the contaminated soil thereby speeding up the natural groundwater leaching

process. The now chemically contaminated wash solution is processed through

a mooile water treatment unit where contaminants are removed. Chemical

additives are then introduced into the cleansed wash solution which is

reinjecten into the contaminated area for further treatment.

Preliminary testing of the mobile in situ soils treatment system has been

completed and shakedown testing is now under way. The unit is scheduled for

field evaluation in 1983.

~v ;T '

Figure 12. Mobile in situ soils treatment system for cleaning and

detoxifying subsurface contaminatetd soils in place by

water-flushing with additives, or by chemical reaction.

Other Technologies

The devices described in the preceding paragraphs are but a few of the

items of emergency response hardware developed under the EPA Oil and Hazardous Materials Spills (OHMS) Branch research program. Other outputs of the

program worthy of mention include the following:

- A trailer-mounted multi-purpose gelling agent system for solidifying and

immobilizing spilled hazardous liquids and preventing their penetration

through the soil into groundwater supplies (17,18).

- A pallet-mounted emergency collection bag and pumping system, consisting

of a 26,500-liter (7000-gallon) furled Teflon-coated urethane bag and

battery-powered or explosion-proof gasoline motor-driven pumps, for

temporarily storing spilled hazardous chemicals (10).

275
- Portable field kits for use by spill response personnel to detect and

identify a wide variety of spilled chemicals in water bodies (19,20).

- Enzyme-based systems for detecting the presence of spilled organophosphate and carbamate pesticides in water (21,22,23).

- A cyclic colorimeter--a device capable of performing opacity-sensitive

determinations for the detection of spilled heavy metals in water (24).

- A field test kit for screening the contents of chemical waste drums at

uncontrolled disposal sites for the presence of strong oxidizing and

reducing agents (25).

- An ultrasonic device for locating sunken insoluble ha ardous materials on

the bottoms of water bodies (26).

- A computerized file of case history information whichidocuments past

field experiences of actual hazardous material incider ts and provides

easy retrieval of lessons learned (27).

CONCLUDING REMARKS

The development of effective emergency response technologies to control

hazardous chemical releases at spills or waste sites is critical to EPA's

mission to guarantee the protection of public health and &ne environment from

the adverse effects of such chemical releases. A point has now been reached

wnere several devices have been designed, constructed, ano field tested.

More will soon be available for actual use. As new equipment is developed,

the OHMS Branch will continue to (a) conduct comprehensive shakedown testing

to ensure field readiness and reliable performance on a rapid response basis;

(b) conduct field trials to demonstrate operational capability and usefulness

of the equipment in "real world" emergency situations; and (c) actively

encourage comnercialization of the new technology by making detailed plans,

specifications, and design drawings available to the private sector.

Although the OHMS Branch research program is predominantly hardware

oriented, its outputs also consist of technical reports, handbooks, guidance

documents, and user manuals on a variety of emergency response-related areas

including: protocols for ensuring personnel safety at waste sites and spills;

practices for reducing the frequency and severity of spillis; techniques for

halting the release and spread of contamination to the surrounding water, air,

soil, and sediments; methods for congealing spilled hazardous liquids and contents of damaged drums; procedures for characterizing the extent of hazardous

material releases and for locating subsurface spills; techniques for controlling spillage from impoundments and waste lagoons; methodology for determining

cleanup priorities and for evaluating alternative removal itechniques; strategies for emergency contingency planning; methods for onsite encapsulation or

destruction of hazardous substances recovered at spills or waste sites; and

rapid emergency procedures for chemical analyses aboard mobile laboratories.

The technology developed under this program is transferred to the general

public via the above documents as well as the biennial National Conferences

276
on Control of Hazardous Material Spills. EPA takes a lead role in organizing

and promoting these conferences which are co-sponsored by other Federal agencies and private industrial organizations such as the U.S. Coast Guard and

the Chemical Manufacturers Association, respectively. The Proceedings of

these conferences are an excellent means of communicating the developments of

the EPA emergency response research program to the user community (28-33).

DISCLAIMER

This paper has been reviewed by the Municipal Environmental Research

Laboratory - Cincinnati, U.S. Environmental Protection Agency, and approved

for publication. Approval does not signify that the contents necessarily

reflect the views and policies of the U.S. Environmental Protection Agency,

nor ooes mention of trade names or commercial products constitute endorsement

or recoumendation for use.

ACKNUWLEDGEMENT

The author sincerely thanks Dorothy Taylor, U.S. EPA, OHMS Branch, who

patiently anu pleasantly typed this manuscript.

277
4-,

REFERENCES

1. Bennett, G. F., and Wilder, I., "Evolution of Hazardous Material Spills

Regulations in the United States," Journal of Hazardous Materials, Vol

4, No. 3, January 1981, pp 257-269.

2. Bennett, G. F., Feates, F. S., and Wilder, I., "Hazaraous Materials

Spills Handbook," McGraw-Hill Book Company, New York, NY, 1982,.pp 2-2

through 2-9.

3. "Oil and Hazardous Materials Simulated Environmental Test Tank (OHMSETT)

Capability," U.S. Environmental Protection Agency, Municipal Environmental Research Laboratory, Oil and Hazardous Materials Spills Branch,

Edison, NJ.

4. Smith, G. F., and Lichte, H. W.,'"Summary of U.S. Environmental Protection Agency's OHMSETT Testing, 1974-1979," EPA Report No. 600/9-81-007,

U.S. Environmental Protection Agenc), Cincinnati, OH, February 1981.

5. "Environmental Emergency Response Unit (EERU) Capability," U.S. Environmental Protection Agency, Municipal Environmental Research Laboratory,

Oil and Hazardous Materials Spills Branch, Edison, NJ, April 1982.

6. Gupta, M. K., "Development of a Mobile Treatment System for Handling

Spilled Hazardous Materials," Report No. EPA-600/2-76-109, U.S. Environmental Protection Agency, Cincinnati, OH, July 1976.

7. Gruenfeld, M., Freestone, F. J., and Wilder, I., "EPA's Mooile Lai and

Treatment System Responds to Hazardous Spills," Industrial Water

Engineering, Vol 15, No. 5, September 1978, pp 18-23.

8. "Acoustic Monitoring to Determine the Integrity of Hazardous Waste Dams,"

Report No. EPA-625/2-79-024, U.S. Environmental Protection Agency,

Cincinnati, OH, August 1979.

9. Friel, J. V., Hiltz, R. H., and Marshall, M. D., "Control of Hazardous

Chemical Spills by Physical Barriers," Report No. EPA-R2-73-185, U.S.

Environmental Protection Agency, Washington, DC, March 1973.

10. Hiltz, R. H., and Roehlich, F., Jr., "Emergency Collection System for

Spilled Hazardous Materials", Report No. EPA-600/2/77-162, U.S. Environmental Protection Agency, Cincinnati, OH, August 1977.

11. Zaccor, James V., "A Mobile Stream Diversion System for Hazardous Materials Spills Isolation," Repcrt No. EPA-600/2-81-219, U.S. Environmental Protection Agency, Cincinnati, OH, October 1981.

12. Kirsch, M., Melvold, R., and Vrolyk, J., "A Hazardous Materials Spill

Warning System," Report No. EPA-600/2-81-212, U.S. Environmental

Protection Agency, Cincinnati, OH, October 1981.

78•
13. Brugger, J. E., Yezzi, J. J., Jr., Wilder, I., Freestone, F. J., Miller,

R. A., and Pfrommer, C., Jr., "The EPA-ORD Mobile Incineration System:

Present Status," Proceedings of the 1982 Hazaroous Materials Spills

Conference, Milwaukee, WI, April 1982, pp 116-126.

14. Griwatz, G. H., and Brugger, J. E., "Activated Carbon Regeneration Mobile

Field-Use System," Proceedings of the 1978 Hazardous Materials Spills

Conference, Miami Beach, FL, April 1978, pp 350-355.

15. Scholz, R., and Milanowski, J., "Mobile System for Extracting Hazardous

Materials from Excavated Soils," Proceedings of the 1982 Hazardous

Materials Spills Conference, Milwaukee, WI, April 1982, pp 111-115.

16. Huibregtse, K. R., and Kastman, K. H., "Development of a System to Protect Groundwater Threatened by Hazardous Spills on Land," Report No.

EPA-600/2-81-085, U.S. Environmental Protection Agency, Cincinnati,

OH, May 1981.

17. Michalovic, J. G., Akers, C. K., King, R. W., Pilie, R. J., "System for

Applying Powdered Gelling Agents to Spilled Hazardous Materials,"

Report No. EPA-600/2-78-145, U.S. Environmental Protection Agency,

Cincinnati, OH, July 1978.

18. Michalovic, J. G., Akers, C. K., Baier, R. E., Pilie, R. J., "Multipurpose Gelling Agent and its Application to Spilled Hazardous

Materials," Report No. EPA-600/2-77-151, U.S. Environmental Protection

Agency, Cincinnati, OH, August 1977.

19. Silvestri, A., Goodman,, A., McCormack, L. M., Razulis, M., Jones, A. R.,

Jr., and Davis, M. E. P., "Development of a Kit for Detecting Hazardous

Mdterial Spills in Waterways," Report. No. EPA-600/2-78-055, U.S. Environmental Protection Agency, Cincinnati, OH, March 1978.

20. Silvestri, A., Razulis, M., Goodman, A., Vasquez, A., and Jones, A. R.,

Jr., "Develupment of an ideitification Kit for Spilled Hazardous Materials," Report No. EPA-600/2-81-194, U.S. Environmental Protection

Agency, Cincinnati, OH, October 1981.

21. Goodson, L. H., and jacoos, W. B., "Rapid Detection System for Organophosphates and Carbamate Insecticides in Water," Report No. EPA-R-2-

7Z-010, U.S. Environmental Protection Agency, Washington, DC, August

1972.

22. wouson, L. H., and Jacobs, W. B., "Evaluation of CAM-l, a Warning Device

for Organophosphate Hazardous Material Spills," Report No. EPA-600/2-

77-219, U.S. Environmental Protection Agency, Cincinnati, OH, November

1977.

23. Goudson, L. H., and Cage, 8., "CAA-4, Portable Warning Device for Organophosphate Hazardous .iaterial Spills," Report No. EPA-600/2-80-033,

U.S. Environmental Protection Agency, Cincinnati, OH, January 1980.

-Io
24. Bock, 0., and Sullivan, P., "Selected Methods for Detecting and Tracing

Hazardous Material Spills," Report No. EPA-600/2-79-064, U.S. Environmental Protection Agency, Cincinnati, OH, March 1979.

25. Turpin, R., "Oxidation/Reduction Potential Field Test Kit for Use at Hazardous Material Spills," Proceedings of the 1982 Hazardous Materials

Spills Conference, Milwaukee, WI, April 1982, pp 225-227.

26. New York Times Newspaper, "Missing Chemicals Found in a Lake in

Mississippi," New York, NY, September 28, 1981.

27. Meyer, R. A., and Stone, W. L., "Development of a Hazardous Substance

Incident Data Base for Response Personnel," Proceedings of the 1982

Hazardous Materials Spills Conference, Milwaukee, WI, April 1982, pp

381-387.

28. "Procgedings of the 1972 Hazardous Materials Spills Conference," Houston,

iX, March 1972.

29. "Proceedings of the 1974 Hazardous Materials Spills Conference," San

Francisco, CA, August 1974.

30. "Proceedings of the 1976 Hazardous Materials Spills Conference," New

Orleans, LA, April 1976.

31. "Proceedings of the 1978 Hazardous Materials Spills Conference," Miami

Beach, FL, April 1978.

32. "Proceedings of the 1980 Hazardous Materials Spills Conference," Louisville, KY, May 1980.

33. "Proceedings of the 1982 Hazardous Materials Spills Conference,"

Milwaukee, WI, April 1982.

280
LEGAL RESTRICTIONS AND PRESENT CONDITION OF

DREDGED MATERIAL DISPOSAL IN JAPAN- ',

Atsushi Sugiyama

INTRODUCTION

At the previous meeting; the U.S. delegates presented several papers on 4

the increasing difficulty inidredged material disposal and new techniques for

the solutions. The PIANC and other agencies proposed that the regulations of

the London Dumping Convention (LDC) concerning disposal control be reviewed.

In Japan, however, no. problem has arisen from the implementation of dredging under the restrictions placed by the L.D.C. and relating domestic laws. 4

Legal restrictions and the present condition of dredged material disposal in

Japan are outlined in the following sections.

LEGAL RESTRICTIONS

When dredged material produced by port works is dumped into reclamation

sites or the sea, dumping is controlled by the Law relating to the Prevention

of Marine Pollution and Maritime Disasters (see Figure 1).

Prior to dredging, the material to be dredged is classified into the following three categories based on the results of the legally obligated solubility test on toxic substances (alkyl mercury, mercury, cadmium, lead, organic

phosphorus, hexad chrome, arsenic, cyanide, PCB, copper, zinc,and fluorides):

I) Dredged material which releases either copper or zinc or a fluoride

exceeding the standairds levels.

2) Dredged material which releases any toxic substance other than copper,

zinc, and fluorides exceeding the standards levels. 7

3) Dredged material other than those listed above.

When using the dredged material classfifed "i" in reclamation work, it

must he made sure that the dredged material and seawater do not flow out into

the sea and drainage standards provided separately must be met for overflowing_ I

water. Ocean disposal is permitted only for specified areas (Figure 2) after

hardening those materials.

Dredged material classified "2" must be dumped in disposal sites isolated

from the sea by watertight bulkheads. Though it may also be disposed of in the

I

281

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C) = C) =) --4 41 0z0 r- 0

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(n -, 41 : 0 0 0 a J 0 w- -- 0 Q X.,

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to u4 V 3 

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above-mentioned specified are-s after hardening, ocr n disposal of those that

contain alkyl mercury, mercury, cadmium, or PCB is prohibited.

The dredged material of category "3" may be used for reclamation work,

provided it does not flow out into the sea; ii may be disposed of at any sea

area.

The above restrictions apply to the methcd of dredged material disposal.

With bottom sediment that contains more mercury or PCB than the specified concentration, we take appropriate measures to improve the water environment, if

necessary. This type of bottom sediment must be disposed of in Lhe disposal .0

areas of same type as those for dredged material classified "2".

In Japan, the Public Water-Area Reclamation Law prohibits reclamation not

intended for specific land use. Sediment that contains toxic substances is

used for reclamation after taking adequate environmental measures.

PRESENT CONDITION OF DREDGED MATERIAL DISPOSAL

In 1981, the dredged material produced by the government-related port

works totalled 27 million m3 in Japan. Almost all of it resulted from3 th?

dridging of navigation channels and mooring basins, of which 900,000 m resulted from port pollution prevention works such as the removal of the bottom

sediment polluted by industrial wastewater, etc. Of this, about 15% or ."-

3 130,000 m contained mercury or PCB exceeding the standard levels described

earlier and thus required removal.

The remaining 95% of the dredged material from port pollution prevention 6

works, and that.from navigation channels and mooring basins hardly contained

toxic substances. Therefore, the ocean disposal method could be adopted in

accordance with the regulations. Tn reality, however, most of it was used for,

reclamation. The dredged material from riv,.-s and fishing ports was also

mostly used for reclamation. The reasons for this were: 1) agreement with

fishermen was extremely difficult with regard to otfskorr disposal, 2) itý

was more economical to use it for reclamation than to transport it offshore.

In addition, there is a strong demand for reclaimed land in densely populated

metropolitan areas due to the shortage of land.

2..

S
ECO-KINETIC MODEL, FOR THE ACCUMULATION

OF PCB IN MIARINE FISHES

Joseph M. O'Connor

John C. Pizza

INTRODUCTION

Contaminant loads to the marine ecosystem adjacent to New York anid

New Jersey Lave beten well documented (Mueller et al., 1976; Maincini et

*al., 1982). Among the more important are the polychlorinated biphenvis,

(PCBs), due primarily to their abundance in the Hudson-Raritan syxstom

(O'Connor et al. , 1982; Bopp et al. , 1981 ), their toxicity (Nait ioalll

* Academy of Sciences, 1979), and their potential to cause chroniiic of focts

inl an ita1il and human populat ions (Kurat-Sune et al ., 1976: Mehrle et al.,

Most of the 1'CBi contaminat ion in the New York B i ,ht derives fromT

oceanl dumnp Inc Of selwagýe slidcL. and waste dredc-ed -vaterial (Taible 1).

'Ahen ro Liti ye PCB cont r ibut ion from di£rect disc ha rces is, cons ide rod and

intecrated accord in4 to typ icalI flow patterns in the Hictex-poted

waitor concent rat ions should ho iglreatest ill the vicin'i ty of the N.Yt.

H il,,ht oceian disposal sites (Figure 1). Actual data from at ,%iriotv of

stud ies show this to he the Case (Fivure 21). Based upon luliin

from lavo laro (1 9821) and O'Connor (,unpubll shled) , we have conc luded th

the olovatedI PCB levelIs to he expucted near the Bight dumpsites diriv.

inroucý-h I eq lal port ions f rom dredved mater iail and sewage sI ude 1The

inicreasted PCB le-vo'ls to the wattr column increaise. the potentiail tor PC 1h

tip take in all t roph ic levelIs (if the Hi ght ~cosystem (Wvman1 and

t)'Connors, luMO0; >,ilifano et al.,* 198!; Brown et al. , 1982';.

:he majoritv Of PU:B p laced in the B ight %vst em with dred ,ed ;ite

rial remains isoitdwith depo-;ited part icu-atv-s.. Cor ing su r

the !red,-ed 7iat or i .1 duml site in the New Yo rk B i;,,ht (NYt3C , 11)82) Oiov

thait }'(i leve ls':air' with devpth of core. The PUBR levels, at dc:,th in

'1l n % cur's 'wk-ro'*'ii~l to levels f ror v,.rious dredc ing pro Vc: s.

, i toro et ai1. (i.1 Press) haive shoiowm thait 1lUB moil i/i tatI.n f ro:i ;'. t' L ~s-diment- sis in..w, on the ordeor of m 11 invters per Vv.ar. 11111 oco

* ~~tri ht in of dred.L-ed L-n..terlial to lT.9 lt-'els in the N,,w York 'h-voe

Q0~1-r-n is aioiit' rimairily with losses- which occur tluriuiiý, dý7

u; r'cetsL;. i vrlIoro (W082) has c-ýit hratkd i lr.- miss loso! !ill -

Jo'' ior;t:3 o-t-; tldir incý dump iný 7i a'. be Oil the or lor a!f

*''i t h -oo. roi'.;':i. ýit hi' ',ev: roti lihi' t hat i i''t vi it,,;: t ' -ýI

T11 ýIt itlk-i;'t t< ,;trm io'hw !red,-od ar~1,utpn

6S
"Table 1. Direct PCB Inputs to N.Y. Bight Apex, in Kilograms per Year

* Source Max. % Total Min. % Total

SAtmospherica 490 7 34 1

b

Municipal Wastewater 42 0.6 42 1

Dredged Materialac 3500 51 i800 61

Sewage Sludged 1300 19 750 26

Hudson Plume (part.) 1037 15 62 i

Hudson Plume (dissolved) 480 7 240 8

Totals 6849 99.6 2928 99

SAssumes 1.14 m/year precipitation at 15 (min) and 215 (max) ng/Q. PCB.

b 99.1 MUD direct wastewater flow; all secondary at 0.3 ug/Z PCB.

From Bopp et al. (1981; min) and O'Connor et al. (1982; max).

d Based upon estimates from West and Hatcher (i980), Sapp et al. (1981),

arJ O'Connor et al. (1982).

SPlume flow assumed to be 6.6 x 10 1 /day, carrying 3 (min) and 50

(max) mg/- solids at 0.86 LglZ PCBs for particulate load, and 10 ng/t

(min) and 20 ng/k (max) for dissolved load.

4

I

I"
Ne

* Figure 1. Generalization of a respotise surface generated by

4 simultanleous mixin4 of PCB inputs to the Bight with relative

concentrations (if the contaminant shown by height above the

planar surface

4* 4-

066l
PCB body burdens in fishes, several investigations have evaluated the

rates and routes of PCB transport in marine ecosyst~ms. Once transport

*- mechanisms are understood, predictive models may be formulated regarding

the extent to which PCBs in sediment may cause increased body burdens.

If a positive relationship leading to unacceptable burdens (e.g., I ig/g,

5 Lg/g) can be related to mud dumping, managers and regulators can take

steps to reduce or eliminate the problem.

Since the early 1970's it has been thought that fishes accumulated

PCB directlyfrom water (Hamelink et al., 1971; Needly et al., 1974).

Experimentally derived bioconcentration factors (3CF) predictive of

*. steady-state burdens in fishes have been published widely (Table 2);

uptake mechanisms based upon octanol-water partition coefficients and

lipid solubility of PCB have been proposed (Needly et al., 1974; Mackay,

1982).

Several factors mitigate against the equilibrium partition theory

as the complete explanation for PCB burdens in marine fishes. First,

the con.ýzpt was developed using pure, dissolved compounds in relatively

particle-free water. Under natural circumstances, seawater contains

many particles to which PCBs are likely to sorb (Hiraizumi et al.,

1979). For striped bass (Morine sa.rat;'s), Califano et al. (1982)

showed that the presence of particles in bioassay water decreased the

quantity of PCB available for uptake, and that body burden was directly

related to "available" PCB rather than total PCB.

Second, published BCF data generally derive from experiments of

long duration, > 5 days. Thus, organisms must be fed during the test,

and the proportion of the PCB accumulated through contaminaced food was

not accounted for in these designs. Many studies have shown that food

material, both living and dead, accumulates PCB rapidly (Wymar and

O'Connors, 1980; Peters and O'Connor, 1982), providing a secondary route

of PCS uptake in the test chamber. Peters and O'Connor (1982), for

example, showed that J.z'imziri and .VYo-dij, common striped bass food

organisms, accumulated up to 2 wg/ý' PCB from water in less than 10 hrs

of exposure to a concentration of I ý.g/i. Inanimate food may accumulate

PCB just as rapidly. Under such circumstances, BCF values calculated

"from long-term exposures almost certainly include a dietary component

not accounted for in application of the data to equilibrium partitioning

theory.

lliird, and perhaps most importantly, equilibrium partition calculations for PCB bioconcentration wenerally yield estimates which are low,

relative to field obse.iations (table 3). Given the potential importance of P'CB in natural systems, we feel it is unwise to rely heavily

upon such "order-of-magnitude" estimates. y;iven the knowledge that all

parts of the marine food web contain 11t:B (MacLe.ad et al., 1981. O'Connor

et al., 19H2), and that cross-gut assimilatiotn of PC8 in fishes approximates 90' (Pizza, 1982), we stress that PCB in fishes derive in some

288
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00

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CC) 04

1--4

28
.4

Table 3. Calculation of Expected PCB Body Burdens in Fishes from

Equilibrium Partitioning Based upon New York Bight Data

Min Max

. Water cclumn PCB concentration (ng/Z)a 10 40

Particulate/dissolved ratiob 0.67 0.67

I Dissolved (available) PCB (ng/Z) 6.7 27

' Bioconcentration factorc 1 x 104 x 10

d Expected concentration (ug/g fish) 0.07 0.27

Observed concentrations (,g/g)e

Striped bass 0.6-3.8

Winter flounder 0. 1

Atlantic mackerel 0.5-0,7

Bluefish 0.7-3.6

American eel 0.5-0.8 I

Tautog 0.6

a - Concentrations derived from Lee (1977), Lee and James (1978), TEC

- (1981), Pequegnat et al. (1980), and MacLeod et al. (1981).

p* b Various authors suggest particulate/dissolved PCB ratios ranging from

zero to about 1. Based upon suggested values from Brown et al. (1982),

Nau-Ritter (1980), and Pavlou and Dexter (1979), we arrived at a value

wherein two thirds of the total water column PCB may be in the dissolved state.

S ~ c

c Based upon chronic bioassay data wherein values range from 1.7 x 104 to

6.1 x 104 (Table 2) for various species. Assuming some fraction to be

associated with feeding, we suggest I x 104 to be a reasonable and conservative BCF approximation (see text).

d

* Calculated as (g/g PCB in water) x BCF, wherein the water value equals

ng (g x 10-9) : 1030, the weight of I ; of seawater at 30 parts per

thousand salinity.

Data from O'Connor et al. (1982), N. Y. State DEC (1981), and sources

cited therein.

9

290

I
"significant part from the food; recently published models for contaminant transport in fishes and plankton demonstrate that dietary sources

may be the prime determinant of PCB body burdens (Thomann, 1981; Brown

et al., 1982) (Figure 3).

°..'

T Tr) X('.AN TOXICAtrIoXICON " I Fiue3 chmtco th odcan 1oe sdb

.' C¢.C• %•• a ro~i 0..! "'s,. COCE -41-=ATIO 10-14, Colic E N TPA TIoN P'-- _ C•,e ONCEN, RAT 0N

* 192 180 Califn ,4) 18 Pi 12 Pz 198 Pz a1 n q 4

SI =V~LA•LE O'%OlVOE-1•CALr

O'Connor, 1982 ~ Caifn ~ ~ ~ adOonr, P~rcýI_ MS in eiw. Th eane

ot Figure 3. Scprovidesothersts of oue food chain modet used by

Thomann (o98r) for evaluating the fate of microcon-

" cp e taminants in aquatic syst ios

Studies of PCB uptake from diet have been carried out in our

""laboratorf for a variety of fishes and crustaceans (Califano et al., _ ~1980, 198'2; Califano, 1981", Pinkney, 1982;, Pizza, 1982; Pizza and

O'Connor, 1982; Califano and O'Connor, MS in review). The remainder

of this paper provides the resulths of our food chain transport studies

of PCB in striped bass. Utilizing these data, we propose a seasonally

variable model to predict dietary acciunulation of PCB in fishes. The

Sconcepts presented here are based upon pharmacokinetic relationships

S(Goldstein et al., 1974). P')ar-acokinetics have been applied to ques-

-" rions of pesticide uptake in fishes by Krzeminski et al. (1977) and

similar principles underlie the recent work of Thomann (1981) in his

efforts to model PCB and cadmium accumulation in fishes.

METNODS

The tochniques used in these studies were developed by Califano et

al. (1982) and by Pizza (1982). Complete details of the pharmacokinetic

approach tLk PCS studies are available in Pizza (1982); see also Pizza

291

3
and O'Connor (1982). To summarize, an evaluation of the assimilation

and excretion of a compound requires empirical data as to the rate of

assimilation from the absorption site (Ka), and .the rate of loss of the

compound (Ke) from some physiological pool; the pool we used was the

entire body mass of the subject organism. The mathematics are straightforward, and based in both cases (Ka; Ke) upon the exponential expression for a decay curve:

M M e-Kat (for absorption) (I)

where M. is the quantity of PCB placed at the absorption site, M is the

quantity remaining at time t, and K a is the absorption rate constant.

Elimination rate constants (Ke) are derived from the same expres-

"sion with different notations: e

X XeKe (2)

where X0 is the whole body PCB level at time zero, X is the whole body

PCB burden at time t, and K is the elimination rate constant. e

Values for PCB assimilation were determined by force-feeding

striped bass known quantities of 14 C-labeled PCB (Aroclor 1254) in

natural food, and sampling at fixed intervals to determine: 1) the

* . quantity of PCB in the gut; 2) the quantities of PCB in the whole body;

"and 3) the quantities of PCB in fecal-material. Sampling of fishes continued for a period of 120 hrs. Tissues were analyzed for total 14 C-PCB

by liquid scintillation counting (Pizza, 1982).

Separate experiments were conducted to determine Ka and K. from

single and multiple feedings. Manipulation of the empirical data conformed to treatments suggested by Goldstein et al. (1974). The equations are documented in Table 4.

RESULTS

When striped bass were given single doses cf PCB there occurred

init'al and rapid elimination from the alimentary tract rollowed by a

phase oC iess rapid elimi.iation (Figure 4). The whole body burden (Figure 5) remained monophasic. Note that, after 48 hr, when alimentary

tract burdens were <10% of the dose, the whole body burden was high,

reflecting nearly complete assimilation cf PCB from the natural food

matrix. For a single PCB dose, the body ourden will follow a time

course reflective of the ratio Ke /Ka , as shown in Figure 6.

292
Table 4. Pharmacokinetic Expressions Applied to PCB Dietary Uptake

Studies

-K t

A. Absorption rate (K ) M = M e a

-K t

B. Elimination rate (Ke) X = X e e

e

-in 0.5 C. Absorption half-time t1⁄2 t-, '2 K

a

-K tK -K t

D. Fractional absorption-single X/M = 1/[(Ke/Ka)_l](e e a_e e

dose 0

E. Time to maximum absorption - tmax 2.3/(K -K ) log K /K

single dose (Ka # Ke ) a e

K /K -K

F. Maximum fraction absorbed - X /M = (K a/Ke) a e a

single dose

-K t* -K t* e e 2

H. Body burden at end of dosing X = X e + X (e ) +

interval - multiple doses 0 0

-K t* + x(e e )n

-K t*n -K t*

H. Body burden after dosing - X =X (1-e e )/(1-e e)

multiple doses n 0

K t*

I. Plateau (steady-state) X X /1-e e

burden - multiple dose

-K t*n

J. Fraction of plateau at f =-e e

"n" doses

293
I

100'

Slope= -0.0494

T

• t

CL

1 1 I I I I f I

0 24 48 72 96 120

Time (hr.)

Figure 4. Percent unabsorbed dose as a function of time. PCB

removal from the alimentary tract as determined by ýo pro-

-I cesses: 1) absorption of administered dose (slope -0.0494);

and 2) elimination from tract tissue (slope = -•.0021)

1000 K

Slope= - 0.0024

2_ loc IC

i t 1 II I I

0 24 48 72 96 120

Time (hr

Figure 5. Percent dose in body as a function of time. PCB

elimination from whole body implying single compartment

kinetics

294
1. .Ke/K =Oz

S08. KO0 .1136 hr" Ke0.C055 hr

I KC/Ket 20.6 Ke/K,(005

Mommurn Absorbed 857% I 28 hr

C.6

S0.4

0.2 / Ke/K=O- 50 II

0

KQ 0 0.2' 0.4 i 0.6 0.8 .0 2 i 1.4 .6 1.81 2.0

ITire •hr) 0 48 96 144 192 240 288 336

1 Figure 6. The fractional absorption of a single dose by first-order

absorption and elimination. The solid curve was determined as in

Table 4 and the data of the current study where Ke/Ka = 0.05. A

maximum of 85.7 percent was absorbed by 28 hr. The other curves

are presented for comparison (Goldstein et al., 1974) at the same

Ke. The case where Ke/Ka = 0 (Ka =) is attained by constant input

rate. For Ke/Ka = 0.50, where for a Ka smaller than that of the

* solid curve, a lower maximum would be attained at a later time

Fishes in contaminated environments, however, do not accumulate PCB

as single, isolated dietary doses. Rather, they contain PCBs derived

from water uptake and they receive multiple, sequential doses of PCB in

food. Our multiple dose study showed the gradual approach to plateau

(Figure 7) expected for young str'?ed bass exposed to sequential doses

of PCB in food at 48-hr intervals. The interval was chosen in order to

observe the approach to steady-state. This is unrealistic, in that the

feeding interval in nature is more likely to be twice each day. Mathematically, this is unimportant; what is essential is that the kinetics

Sof the system (see Table 4) show plateau reached at dose n = 17. For a

fish feeding twice each day, plateau would be reached in 8.5 days.

APPLICATION TO MODELING

Thomann (1981; see Figure 3) documented clearly the level of com- plexity required in meaningful models of contaminant accumulation in

fishes. In his model he noted: P) the lack of data relevant to the

function referred to as the "food-chain multiplier"; and 2) the need to

account for age-specific changes in respiration, feeding, and growth as

determinants of predicted PCB body burdens in striped bass. In the

preliminary model presented here, we provide the food-chain multiplier,

as influenced by growth of the fish, changes in metabolism, changes in

food ration, and changes in dietarv PCB levels.

2

295
1600- X

R90%X, ~~~-- 1200 -

S800

4C0'

Time (hr) 0 48 96 144 192 240 28 336 384 432 480

DoseNumber I 2 3 4 5 6 7 8 9 10 It

Figure 7. Curve for the cumulative retention of PCB from

multiple dosing. Solid lines present actual levels

attained during experiment. Dashed lines are the calculated extension of the data. The plateau burden (X.) is

the steady-state level attained from peak values after

sufficient dosing (see text)

Pizza's analysis (1982) of striped bass PCB accumulation from diet

revealed that changes in plateau PCB burden depended upon two factors.

The first is the Ke. The second is the dosing interval at which new PCB

is taken in via the food. The relationship between physiological growth

in the striped bass and required ration size, as well as weignt-specific

metabolism, is depicted in Figure 8, along with the expected effects

that changes in these factors may have on food assimilation efficiency

and the elimination constant (Ke) for FCBs (Califano et al., 1982; Pizza

and O'Connor, 1982). The physiological data suggest that, for a growing

fish, there should be no steady-state PCB level; since metabolism (and,

hence, Ke) declines with age, and since assimilation efficiency declines

with increasing age and ration required for growth incraases, the PCB

body burden should increase continuously. Further, since the volume of

water required for oxygen exchange must increase with size, more direct

water uptake of PCB is possible. The importance of the latter in contributing to body burden may be questioned, however, since respiratory

requirements may be extremely variable depending upon ambient levels of

dissolved oxygen, temperature, time of day, time in the feeding cycle,

etc. (Neumann et al., 1982).

The pharmacokinetic model incorporated these relationships under

conditions representative of striped bass biology in the Hudson estuary.

fhese were:

1. Active feeding during the first growing season on zooplankton

containing 5 'ig/g (dry weight) PCB (O'Connor et al., 1982). --

2. A growth rate of 0.02 d

296
I

%C

S/ .~ diS

0 -C '-S.-"--S.

E /...*

Size - ze

Fi-gure 8. Schematic representation of t1 : respo se of various

-lvphvwiologica•i pnr.me~ters to increaised s8: .! L e organism.

Tn the left figure, required ration to g ow J res,;piration

(,.ýg 01 per hour per indlvidu:il) fncr-ias . increased s 17e;

assimilat~on efficiency of food decreases. In the right

figure, metabolisr- and elimination-constarit K decrease wIth

increasing size

3. Decreasing K -.t a rate proportional to weight; W0* 7 /W (Brett,

1979).

4. Increased ration sire to maintain a daily intake of 107 body

weiht .

3. A feeding interval of 12 hr, with one-half the daily ration

(and PCB dose; consumtd during each feeding period.

6. Additional feedi'%, 2'uring the sLconJ growing season on zooplankton cont.tinlng, 0.5 "g/i (dry weight).

7. An optional "overwintering," period during wh!ch K, do.crtasod

as a lInCtion of tt~wr|tur* (Neuma.inn ot al.,, 1981 ), -und feedi'g was reduced to 4.;-hr i terva (once each two dav%;

Lawler, Maitusky' and Skellv Ingineers. 1 -80).

ihc •ode1 -2 s r'm In t'4Io - .,d gure 9 wn proesent thc outcome

otf tho nodol jncorpDorting, factors I through 7 abov.. Tn modo I (;;olid

lini-p an irtificial O-d. feedin,/growt period was impwed, during,

which the basa, were cnrtt io ti'l expcoi:ed to feod cont.i ink.i', . ./"

P'(2!ý. lode 2 (dashed line) ref l.cts the "'naturail s tuiatiel," fi ;h fod

for one 4rowin'; period on food contalining ).0 ;ig/'PCB,; durint the

297
,4

second growing period (days 150 through 330) the food ccatained 0.5 4g/g

PCB. These values reflect the natural habitat during year It.

The pharmacokinetic model showed that the dietary uptake of PCB

could account for about 3.8 wg/g (dry weight) in ehe course of the first

150-day growing period. This translates to 1.1 Lg/g PC3 (wet weight)

"expected in fishes occupying the brackish water portion of the estuary.

Expected concentrations due to equilibrium partitioning for this portion

of the river (see Table 3) would be \,0.3 pg/g. Califam et al. (1.982.)

showed young-of-year bass from the same river region to contain 1.6 L-g/g

total PCB (wet weight). The dietary component, therefore, could

" represent about 63% of the obcerved PCB burden in young striped bass

from portions of the Hudson where dietary PCB burdens are high.

(;iven.a change in dietary PCB burden from 5.0 to 0.5 ug/g PCB,

which could be accounted for by migration or change in food preference

during a second growing season, we predict a decreased body burden (Figure 9). Following a loss from 3.8 to about 0.5 twg/g (WA - 1) growth,

increased ration and declining K. cause re-initiation of PC5 build-up to

v'O.8 1g/g (dry weight) after a total of 330 d.ays (or I80 days on the

reduced PCB diet). this value ("'•0.2 -g/g wet weight) represents from

32 to 87% of the whole body PCB determined in. year T1 striped bass trem

river regions where food organisms contain A0.5 ug/g (Lewler, Matusky,

and Skelly Engineers, 1980; 0.23 to 0.63 .g/g PCR in striped bass, n -

4). With an expected equilibrium partitioning value of 0.07 to 0.2 iig/g

(lable 3), we conclude that PCB uptake from a diet containing low levels

of PCB remains important to the organismn. Tn no case can equilibrium

partitioning be shown to account for the total PC3 in striped bass.

The effect of reducing dietary PCB intake is dramatic in the model

output. 'Note in Figure 9 that within 30 days the expected body burden

F dropped to about 0.5 •g/g and, with continucd feeding at loy PCB levels,

the Pxpected PC8 burden at day 302 is about 0.8 iig/g. Beyond the final

valtuesa of the prediction, Figure 9 demonstrates several important -ot .ts

relative to ecology, growth, and I'CB accumulation fro, dietary sources.

First is the concept of steady-state. Our results show that,

rg..ardless of PCH source, a steady-state body burden is unlikely to

occur in any environment othier than a controlled chronic bioasmay study

"with no growth. In the real world, any change in PCIB ftatke due to

. change In water concentration or PCB done in the diet will. due to the

"continual change in Ke, result in a shift toward a now plateau level.

Second is the concept oC growth-rolated bio~accumulation fa'-torq.

Tn Figure 9, the findings of mode I and mode 2 model rittts rexult in

0 rat he r d f f vr, nt rates of P'CB b ioaccummu lat ion; however, when viewed

from the perspecti ye of dietary btirdo.i onet' can 'ee that for arev given

point Inm timet, the ratio / /K Is the -4am, for mode I atmd m•t'- 2. 1 he

for vi i, o s I n al ;C t i . raite of accrsr•mul at lon ( V-/dav PCIM ) exist !•.'taus,'

while rate of elimination (Kg,) is a first-order ftinction. the mrowthrelaited decline in Ke will result •n ,cce ler.ation of tOoe ,lccunmnlaLt to n

298
44

3

E

CL

. _ 2

01

- 50 i"1600 1F•0 200 2.0 300 33Q

Days

Figure9. Predic ted PCB accumulation, .as ug/g (dry weight)

PCB In the whole body (if stripeid hass exposed for 330 days

to a diet containing 5.0 ug/' PCB (Mode 1; solid line), and

for 150 d;avs to 5..() ug/g PCB followed by 180 dav, exposure

a diet containinng 0.5 ug/g PCB (Mode 2; dotted line)

rate ais soo•• -is i plateau it reached. At the higher feeding rate, the

curve hais a sh.irp upward& trend. At the lower rate of PCR do. ing, the

acce lerat ion of the raitei I,; ,o'q obvious sincte body burdenns were reduced

rmarked, lv hv the reduced rte oit d,•t,4Iti. and have remnained low during the

ext ended pe'ri(1 of low-level feedi ing.

Tird, mid p,,rhaps tm,,;t Importaint, is eluctidation of the concept of

in I i'm,.dv . •.v -hift t•w.wrd i new plat eaou lvevel wh.n P(CH source termfl

cIr.n.il' thos, r. for ;t ripe,,! blss in ;k n uritulr,il v't, , wher,, water c'ncen-

* t r.it ion- t P'CB iro re•l.t ivilv uniform., one mtnkht expect, the fot klo,'niz

t, b). I rae'

I. St rt;,.d !.m rom ,'c.mi ,nvifronmoits, where 'II l) vT3• in fod

Ar,, .,4, Mhoa & . ntji in lower bodyv Imrdens th-in fi st ; r,

anp' 1',the estlar'rv.

ii drns fi , i-:1 b ,h,,,i!d l h , ,,wr Iiirilnl winter

,,'1,t r pty ':~ ,'rctietau -in a 4h' t-iri i ,,rowth

T, "I . b rI'-; 'I .. d i t,irv

,," ~ ~ ~ '.u ~ ~ e lvercti. -!d 
I

4. Low levels of PCB in the diet (e.g., 0.5 .g/g) will not, in

the course of one growing season, cause body burdens to exceed

present or proposed FDA guidelines for burdens in fishes.

5. Widespread increases in water-column PCB levels could become

important in marine toxicologic-a questions if this were to

increase burdens throughout the food chain and raise waterderived levels by a measurable degree.

6. [he tendency to undergo rapid shifts toward new PCB plateaus

renders localized PCB "hotspots" of minor import in otherwise

"clean" marine systems when the organism in question is

mobile, pelagic, and highly migratory.

The likelihood of verifying these expectations with existing field

data is low; much depends on accurate determination of water and food

chain PCB values, careful sampling of year classes for PCB analysis, and

sampling efforts aimed at the proper location-season-specimen regime.

We have, at this time, undertaken to formulate these expectations as

hypotheses, and are testing them in the New York metropolitan region.

As a final note, we hasten to point out that our empirical and

modeling data have direct application to ongoing ocean dumping studies

as follows:

First, our hypothesis that PCB burden in fishes is strongly related

to diet renders the "mass loading" approach to ocean PCB pollution ineffective in estimating contaminant levels in fish. Both dredged material

and sewage sludtte -must be evaluatvd more carefully to assess real quantities

of PICBs injected into the food chain and the water column.

Second, the pharmacokinetics of T'CBs in fishes suggest that any

*• Isolation of contaminated materials from entry to the food chain will

have the effect of lowering ?C8 body burdens in the large, predatory

species which often form an important part of the human diet. Thus,

maintaining a surficlal layer of sediments with low or nonavailable

C'is will, in all likelihood, result in a trend toward lower body burdens in all trophic levels.

ihird, the overall outcome of the model 4uggests that we shall not

iee increased PCB levels in fishes if input 'ate#S and itnllut source*,

remain similatr to those of recent vear . While we do not .advocite usa,

"" the of min asi unrest r icted duw.ps , we do suggest that, w tf ti me, the

in;p,lt ot h• Iavajilable PC' to New Y.irk mar -one waters has achieved a1 hal-

,11nct-; it ivptears t hat inv i.-mpacts whicih hive occurred are not irreversiI ,) It 1,ail.t'it h the ir detscription i-A linclear. "'rt ,her dumping regilationo s

h,),,Id it1icItad,, a tt ent i ,on to rende r inn such chiCoilnL.t t nt11i. sA S PC, irst

*mlt.i lahl' to •ood ch.a Ins, and, fIn~al l-,, inava.i lahle in the w.tter

300

I
LITERATURE CITED

Bopp, R. F., et al. 1981. Polychlorinated biphenyls in sediments of the

tidal Hudson River. New York. Environ. Sci. Technol. 15: 210-216.

.. Branson, D. R., et al. 1975. Bioconcentration of 2,2',4,4'-tetrachlorobi-

*i phenyl in rainbow trout as measured by an accelerated test. Trans. Am.

Fish. Soc. 10.: 785-792.

Brett, J. R. 1979. Environmental factors and growth. Chapter 10, pp. 599-

675. IN: Hoar, W. S., D. J. Randall and J. R. Brett (eds.). Fish Physiology.

*°"Vol. S. Bioener.ýetics and (;rowth. Academic Press, New York.

Brown, M. P., et al. 1982. A mathematical model of PCB bioaccumulation in

plankton. Ecol. Modelling 15: 29-47.

SCalifano, R. J. 1981. Accumulation and tissue distribution of polychlorinhated biphenyls in earl• life stages of the striped bass, Mom;•:e 8.

Ph.D). Dhesis, New York University, New York.

*, Califano, R. J.. J. M. O'Connor and L. S. Peters. 1980. Uptake, retention p. and elimination of PCB (Aroclor 1254) in larval striped bass, "'o.:,

:"ull. Environ. Contain. Toxicol. 24: 467-472.

Califano, R. J., J. M. O'Connor and .1. A. Hernandez. 1982. FCB dynamics in

Hudson River striped b.ss: 1. Accumulation in early life history stages.

Aquat. joxicol., in press.

DeFoe, D. L.. l'. D. Veith and R. W. Carlson. 1978. Effects of Aroclor 1248 ".. and 12)60 o, the fathead minnow (<-'• , ,'eY;c). J. Fish. Res. Bd.

Canada 35: 997-0GO2.

*.. itoro et al., in press.

(;oldstein, A., L.. Aronow and S. M. Kalman. 1974. Lrtncj.pjes of drug action:

* hebasis of2h~ar~macoloy. I. Wiley and Sons, New York. 854 pp.

llamelink, I. L., R. C. Wavbrant and R. C. Ball. 1971. A proposal: exchange

equilibria control the degr,-e chlorinated hydrocarbons are biologically

maknif ied in lentic environments. Trans. Am. Fish. Soc. 100: 207-214.

•" Hansen, I. ., tet al. 1971. Chronic toxicity, uptake and retention of

Aroclor 12 3,. in two estuarine fishes. Bull. Environ. Contain. Foxicol. ,. b: Iii-119.

,i ra i,:.•i, Y., M. lakahashi and H. Nishimura. 1979. Adsorption of polycolor I natcd bi pnvi onto seabed ;edimentr, marine plankton and other adsorbing

.1V'ntI. Lnviron. Sci. l echnol. 13: 5$U-584.

*I (: rn t;Ite Electronics Corporation). 19S!. Environmental Tmpact

S , t• me: tor New York i)redged Material Ocean I)isposal Site Designa ion.

Rept. to I'. . K1P,. An lheim, Calif.

30 1

S
Krzeminski, S. F., J. T. Gilbert and J. A. Ritts. 1977. a pharmacokinetic

7". model for predicting pesticide residues in fish. Arch. Environ. Contam.

Toxicol. 5: 157-1bb.

Kuratsune, M., Y. Masuda and J. Nagayama. 1976. Some recent findings

concerning Yusho. Proc. National Conf. on Polychlorinated Biphenyls. EPA560/6-75-004, pp. 14-30.

Lawler, Matusky and Skelly Engineers. 1980. Biological and water quality

data collected in the Hudson River near the proposed Westway Project

during 1979-1980. Vol. II. Rept. to N. Y. State Dept. of Transportation.

LMS Engineers, I Blue Hill Plaza, Pearl River, N. Y.

* Lee 1977.

Lee and .lames 1978.

Lee, G. F., et al. 1978. Evaluation of the elutriate test as a method of

predicting contaminant release during open-water disposal of dredged sediments and environmental impact of open-water dredged material disposal.

Volume II: Data report. DM1R' rech. Rept. D-78-45. Environmental Effects

Laboratory, U.S. Army Engineer Waterways Experiment Station, Vicksburg, MS.

1186 pp.

Mackay, 1). 1982. Correlation of bioconcentration factors. Environ.

SSci. Technol. 16: 274-278.

* UacLeod, W. 1)., et al. 1981. Analysis of residual chlorinated hydrocarbons,

aromatic hydrocarbons and related compounds in selected sources, sinks and

biota of the New York Bight. NOAA Tech. Memo. OMPA-6. 128 pp.

M Mancini, J. L. et al. 1982. Urban loads to the New York Bight. IN:

Mayer, G;. (ed.) Eeo1oicalStress and the New York Bight: Science and

Management. Estuarine Research Federation, Columbia, S. C.

Mauck et al. 1978..

" Peters, L.. S. and .1. M. O'Connor. 1982 (in press). Ecological implications of organic contaminants in marine and estuarine zooplankton. IN:

F. May',-r (ed.), Ec.ological.Stre -ssand. the- New York Bight: Science and

- Mail _aýjmetL. istuar inc Research Federation, Charleston, S. C.

lPinknev, A. F. 1982. Uptake and retention of I4C-Aroclor 1254 in rGammartus tlirinus after dietary exposure with the fungus Fusarium -oxvs._-

POrum. M.S. 1hesis, New York Lniversity, New York, N. Y. 70 pp.

I'izza, 1. C. 1"8". Kinttics of I'C3 accuinoilation in Hudson River striped

bass. I'h. 1). llt, sis, New York Universitv, New York, N. Y.

Pizza, .1. C. and 1. M. O'Connor. 118-2. I'CB! dynamics in Hidson River striped

btiss . I I. Acciimuloition from dit. tary sources. VquaL. Toxico•l. in pres ).

302

4
[I

I:" Stallings and Mayer 1972.

"ravolaro, J. 1982. Sediment budget study for dredged material in the

New York region. U. S. Army corps of Engineers, N. Y. District. Federal

Plaza, New York, N. Y.

Thomann, R. V. 1981. Equilibrium model of fate of microcontaminants in

diverse aquatic food chains. Can. J. Fish. Aquat. Sci. 38: 280-296.

West, R. H. and P. G. Hatcher. 1980. Polvchlorinated biphenyls in sewage

sludge and sediments of the New York Bight. Mar. Poll. Bull. 11(5): S~12b-129.

Wyman, K. and H. O'Connors. 1980. inplications of short term PCB uptake

by small estuarine copepods (genus Acartia) from PCB-contaminated water,

inorcanic sediments and ph\'toplankton. Estuarine Coastal Mar. Sci.

11: 121-131.

303

6
*9

ASPECTS OF THE DAMOS

"MONITORING PROGRAM IN

* THE NEW ENGLAND REGION

V.L. Andreliunas

U.S. Army Corps of Engineers

"424 Trapelo Road

"Waltham, MA 02254

ABSTRACT

A synopsis is given of an ocean monitoring

program designed to assess the impact' of disposal of

dredged material. The program extends to sites which

have differing physical characteristics, thus requiring some individualistic treatment. Important criteria

in terms of equipment capabilities are cited, and

measures utilized to monitor physical, biological, and

chemical parameters are lescribed. The use of sentinel

organisms, especially Mytilus edulis, is an important

component in the program design. The program, in its

present state, has been employed for five years in the

New England region.

While the necessity for assessing the state of our ocean waters is

readily endorsed by both the scientific community and body politic, the

means by which this may be achieved continues to be a most difficult challenge. This paper, by tracing the experiences gained over a- fifteen-year

"period by our organization in managing contaminated dredged sediment, may

provide some insight to the many problems which are encountered in monitoring programs.

MonitorIng programs are usually conceived for the purpose of (1) providing warning against imminent harmful impacts from recognized sources, and

(2) evaluating and forecasting long-term impacts. While a single monitoring

* program may well satisfy both of these objectives, the strategies adopted for

each may vary considerably, and may greatly affect the resource requiroments.

However, because monitoring strategies for ocean programs also need to be individualized, both in a geographic sense and to discriminate between specific

influences, there is no simple method to arrive at an acceptable design.

There are many lessons to be learned during the initial period, for which

there appears to be no substitute.

304
Our progress in monitoring programs thus far has been guided by necessity

"for purposes of compliance, and as a tool for management of dredged material.

Notable successes have been in the areas of developing reliable methods, hardware, and technology in the initial phases, which allows greater freedom and

flexibility in addressing demands placed on the program. These successes include

methods for precise measuring of bathymezric change, marking devices for

"guidance and control, tracking and locator devices for control and instrumen-

.. tation, and a well-integrated system of support services. With these in

place, we were able to develop advances in disposal techniques involving

capping (Morton, 1980), as well as to expand the program to encompass the entire geographic area of our responsibility.

While much of our initial activity has centered around the region of Long

* Island Sound, which to some extent represents estuarine conditions, the techniques we found in most cases were readily adaptable to deeper ocean sites.

Too much cannot be said for having a hospitable environment in which to develop one's hardware. Moreover, the depths of water in the sound, 20 to 30 meters,

has allowed for more critical observations by divers of both physical and

biological phenomena than could otherwise be obtained.

The present monitoring program, now known as DAMOS, in the New England

-region has ev'olved over a period of 15 years of observing dredged material

disposal. The program focuses upon 12 disposal areas whose distribution

coincides with the location of major dredging activity. This activity, in

turn, is regulated by the shipping needs of major ports whose commerce is

"predominantly petroleum imports. The sediments associated with this dredging are frequently contaminated by petroleum residues, vai'ious metallic comgenerated by the Spounds industrialized cities, and a variety of other compounds

which include pesticides and chlorinated hydrocarbons. Because the region is

rich in fisheries resources, it is essential not only to avoid conflicts in

disposal area siting, but to provide reassurance to the public that food

sources are not being contaminated.

Each disposal site has been designated after extensive consultation with

fisheries interests, and only after a screening of physical characteristics

and an inventory of biological activity of the location. One attribute of

historically used disposal areas is that many have become prolific lobster

grounds, and in three instances, it has not been possible to regain their use

because of fisherman pressure. Limited studies of lobster populations of historic dumping grounds has revealed no adverse characteristics attributable to

this habitat. Being compelled to abandon dedicated disposal sites,of course,

adds additional pressures to the regulator's task, since lobstering and dumping grounds are also incompatible with other forms of bottom fishing. As a

general and very unprofound statement, I will offer that science cannot begin

until the smoke of political battles has settled.

The protocols now being followed in each area are generally similar with

respect to method, but are also tailored specifically to the depth of water

and exposure conditions, as well 3s to the extent of usage by the dredgers.

These may be categorized into a typical, physical, biological, and chemical

array.

305

- -- ----
Physical monitoring is that which looks for gross or catastrophic effects

due to movement of materials during and after disposal operations, particularly following major storm events. The hardware currently in use was developed

over a period of years to perform the desired function, which is, basically,

to establish a grid over a given area and to replicate accurately measurements

for comparison over time. Our system utilizes an Apple II microcomputer interfaced with a Model 540 Del Norte Trisponder and an EDO Western multi frequency

fathometer system. Data are recorded on "floppy disk" media for rapid acquisition and comparison of data and to allow visual displays for control of the

vessel. Other types of positioning systems such as LORAN-C can be interfaced

to the equipment for more flexibility in the survey, sampling, or disposal

management activities. Bathymetric surveys are run on 25-meter lane intervals, giving more than ample resolution and discrimination of volumetric

changes in disposal mounds.

Utilizing this equipment and methodology our program now has records of

disposal activity in each of the major dumping grounds, beginning with the

pre-disposal condition, during dumping, and at intervals following. This

allows an assessment of any gross physical change together with correlation

to any other observed phenomena on the site. The technique has worked equally

well in Long Island Sound at a depth of 20 meters, and in the Gulf of Maine

at depths of 60 meters. The ability to mairtain consistent records is essential to any evaluation of long-term effects. Morton (1980) has reported extensively on the effect of hurricane force wind-induced-stresses on a disposal

mound.

While current measurement, particularly in the near bottom layers is important to evaluating site conditions, especially in predicting stability of

any deposit, the means of instrumentation over extended periods requires refinement. Our program has had success in'maintaining various arrays of

current and suspended solids sensing equipment which has yielded useful data

(DAMOS ANNJAL REPORT, VOL. I, 1980). However, the reliability of such equipment beyond 10 days is often compromised by marine organism fouling. This

argues for more intensive developmental effort since major meLeorological

events which are the sought after records do not always cooperate with

cruise schedules.

With the amount of information we have acquired to date regarding physical regimes which apply to each disposal site, we are within reach of producing a mathematical model which will be useful to the regulator. As such

models are refined, prediction of resulting bottom conditions and management

response w-.il be considerably improved. If the premise is true that the

physics ot an area governs the biology, then we are not far from what is

theoretically possible in competent prediction of site conditions resulting

from disposal.

The biological component of our monitoring experience has been most

intriguing because of the inherent variability of conditions at our ocean

sites. It seems that everyone has a favorite indicator species which relates pollution effects on living resources to predictability of impact

upor humans. We have, of course, made hundreds of observations of population dynamics, body burden, and other parameters both in the field and in

the laboratory, but choosing the one, or the set, is a most difficult task.

306
There is much to be said for studying fish species which are directly

consumed by man as a monitor of potential adverse impacts. We intend to

expand upon this phase of our activity in future programs as we gain familiarity with appropriate species and background conditions.

For four years now we have been utilizing sentinel organisms at each

major disposal site. The bivalve mollusc, Mytilus edulis, was chosen for

its ubiquity and sessile existence, as well as its recognized commercial

and ecological importance. It has been used by many investigators for some

years, is well Cocumented in the literature, and is the principal organism

used ir the Global Mussel Watch Program. This phase of our program is conducted under the direction of Dr. S.Y. Feng of the University of Connecticut.

His reports on the temporal and spacial variations of trace metal levels,

PCB levels, and physiological conditions of these sentinel mussels are contained in DAMOS Reports 20 thru 22, and the 1980 Annual Report, among

others.

The findings to date encourage us to continue to utilize both the blue

mussel and the horse mussel (Modiolus modiolus) both from the standpoint of

measurable response to changing bottom and water quality conditions, and

from the st..ndpoint of convenience. Given the sometimes arduous conditions

under which ocean monitoring is conducted and the high cost of sustaining

vessel and laboratory operations, any methodology which simplifies the job

must be counted as a blessing.

Feng (1982) in his report on deployment of the sentinel mussels at the

capping experiment site in Central Long Island Sound gives further insight

into monitoring design and strategy. The results of analysis for heavy metals

indicate that peak concentrations tend to occur during periods of increased

suspended load in the water column attributable both to natural meteorological events and dredged material disposal. These observations compare with

sediment transport studies being conducted under the program, which show also

that the temporal and spacial effects of dredged material disposal are several

orders of magnitude smaller than those induced by natual storm events.

These observations further correlate with similar studies conducted in

Eastern Long Island Sound which suggest that the observed temporal variation

of trace metal concentration in mussels is strongly influenced by a variety

of factors such as river runoff.

Since inception of our disposal area studies we have relied a great

deal upon sampling from surface vessels by conventional apparatus with

accompanying analyses of diversity and density of colonizing species. Over

this same period, however, we have compiled an extensive library of underwater photos and diver accounts of observed phenomena which contribute

measurably to understanding sediment behavior and dynamics, as well as

biological activity. Wherever site conditions allow, both diver observation and photography improve tý- confidence level of the program manager

in his interpretation of data greatly, and justify the extra effort and expense where necessary.

307
Chemical analyses are carried on concurrently with all biological

sampling and in conjunction with cores taken on site, both by surface craft

and by diver. As the chemistry data begin to accumulate, we see some interesting relationships which may be of possible significance to later

management activities. In general, the cores taken have been used to confirm visual observations of dredged material transport or mound behavior,

and it is clearly possible to associate material on the dumpsite with its

origin, based on pre-dredging analyses.

Thus we see the possibilities of correlations being drawn from biologi- Scal, physical, and chemical parameters which would allow the manager to

better discriminate between short-term and long-term as well as man-iniuced

versus natural occurrences. This argues strongly for the design of any

program to consider the means by which perceived impacts can be analyzed

from more than one perspective.

An extremely important offshoot of our experience with the monitoring

program was the application recently of many of these techniques to the

selection of a new disposal area in western Long Island Sound. Once the

primary characterization of the region, consisting of commercial fisheries

surveys, overall topography, and wave climate, had been developed, the

process of refinement and definition of optimum conditions was initiated.

Overall bathymetry was evaluated using side scan sonar combined with the

fathometer system to generate a contour chart. The side scan proved to be

a valuable interpretive tool for purposes of identifying bottom sediment

characteristics. The area tentatively selected from these records was extensively sampled to confirm sediment character, and samples were aralyzed

for baseline information. Current meters deployed during the survey, together with wind and suspended sediment data, provided useful comparative

information. Benthic sampling combined with diver transects tended to confirm the bottom conditions revealed by physical measurements. Ultimately,

a bottom feature resembling a trough was considered to afford the optimum

depositional site condition to meet the requirements of regulation and to

avoid conflict with other users. Surveys subsequent to initiation of use

of this site confirmed that the specifications were being met in all

respects (DAMOS, CONTRIBUTION ,,'19 1982).

The interesting relationships to which I refer have intrigued scientists for some time, but have not been pursued a great deal in research.

This has to do with the factithat, because of their potential harmful

effects, attention until now has been directed to detection and measurement of heavy metals and various toAins. There has been a corresponding

neglect of possible beneficial effects that may result from the disposal a

of dredged material at sea.

In our initial attempt to characterize two regimes, the North Atlantic

Tidal System and the Gulf of Maine Tidal System, we have compiled bulk sediment analysis data from cores and grab samples from approximately one hundred

New England harbor bottoms. A natural extension of this analysis would

seem to lie in evaluating the effectiveness of these organic sediments as

fertilizers when they are dumped at sea in fishing ground areas, that is,

h..

308

4 %

* A'• • '"
to examine the sediments by breaking down their organic fractions into

estimates of their various components to see what they might have to offer

by way of enrichment and enhancement of primary productivity. Theoretically, it appears that this could become a strategic component of disposal

site management, with the same degree of predictability that is being

developed for physical attributes.

The intriguing possibility of maximizing the productivity potential

of the ocean bottom of course goes beyond the original objectives cited

for monitoring programs, which were compliance and long--term or trend

assessment. However, it is an indication that monitoring programs are

capable of developing good scientific information in the course of serving

other purposes. It seems to make good sense, considering the high expense

involved in mounting marine studies, to attain optimum benefit from the

effort.

While I have touched upon some of the facets of our program whicb I

believe are distincti've, I must also emphasize that proper organization

and operation of a successful monitoring program involve much more. Quality

control, integration with other programs, possibly of wider scope, and provision for information transfer are equally vital aspects.

The subject of quality control is far too extensive for the purpose of

this paper. It is as much a function of design of the program as are the

other components. Our own experience thus far has been satisfactory on a

regional basis because of the relatively few participants in the program.

Obviously, the correlation of information of one program with another will

require far greater effort on all participants with regard to inter-laboratory

calibration and other considerations.

As a concluding note, I suggest that those who engage in design of

monitoring programs guard against the tendency of scientists to "comparzmentalize" along special disciplines. There is little question that it

is easier to work this way, but it does not serve the project nearly so well as does an organization along inter-disciplinary lines. Our program

has certainly benefited from this principle, as have the individuals who

must utilize its findings.

309

11.-
REFERENCES

Arimoto, R. and Feng, S.Y., July 1982. "DAMOS Mussel Watch

Program, Histological Studies of Mussels from Dredged Material Disposal Sites," DAMOS Contribution #20, Contract #

DACW33-82-D-O001, Science Applications, Inc., for U.S. Army

Corps of Engineers, New England Division, 424 Trapel- Road,

Waltham, MA 02254.

Feng, S.Y., July 1982. "DAMOS Mussel Watch Program, New London

Disposal Site Monitoring Projects 1977-197M," DAMOS Contribution #21, Contract # DACW33-82-D-O001, Science Applications, Inc., for U.S. Army Corps of Engineers, New England

Division, 424 Trapelo Road, Waltham, MA 02254.

Feng, S.Y.. July 1982. "DAMOS Mussel Watch Program, Monitoring

of the 'Capping' Procedure using Mytilus edulis at the Central

Long Island Sound Disposal Site 1980-1981," DAMOS Contribution #22, Contract # DACW33-82-D-0001, Science Applications, inc.,

for U.S. Army Corps of Engineers, New England Division, 424

Trapelo Road, Waltham, MA 02254.

Morton. R.W. and Karp, C.A., 1980. "Disposal Area Monitoring System,

Annual Report," Vol I, Physical Measurements, DAMOS Contribution #17, Contract #DACW33-82-D-0001, Science Applications,

Inc., for U.S. Army Corps of Engineers, New England Division,

424 Trapelo Road, Waltham. MA 02254.

Morton, R.W. and Karp, C.A., 1980. "Disposal Area Monitoring

System, Annual Report," Vol II, Biological Observations,

DAMOS Contribution #17, Contract # DACW33-82-D-0001, Science

Applications, Inc., for U.S. Army Corps of Engineers, New

England Division, 424 Trapelo Roaa, Waltham, MA 02254.

Morton, R.W. and Karp, C.A., 1980. "Disposal Area Monitoring

System, Annual Report," Vol III, Visual Observations, DAMOS

Contribution #17, Contract # DACW33-82-D-O001, Science Applirations, Inc., for U.S. Army Corps of Engineers, New England

Division, 424 Trapelo Road, Waltham, MA 02254. =

Morton, R.W. and Stewart, L.L., May 1982. "Interim Survey of

Western Long Island Sound III Disposal Site," DAMOS Contribution #18, Cnntract # DACW33-82-D-0001, Science Applications,

Inc., for U.S. Arny Corps of Engineers, New England Division,

424 Trapelo Road, Waltham, MA 02254.

310
Morton, R.W., Paquette, G.D. and Stewart, L.L., January 1982.

"Baseline Survey of the Proposed Western Long Island Sound

III Dredged Material Disposal Site," DAIMOS Contribution #19,

Contract # DACW33-82-D-0001, Science Applications Inc., for

U.S. Army Corps of Engineers, 424 Trapelo Road, Waltham, MA

02254.

Morton, R.W. and Paquette, G.D., August 1981. "Preliminary Data

Report Brenton Reef, Wellfleet, Norwalk Disposal Sites,"

Contract # DACW33-81-C-0115, Science Applications, Inc., for

U.S. Army Corps of Engineers, New England Division, 424

Trapelo Road, Waltham, MA 02254.

Naval Underwater Systems Center, May 1979. "DAMOS Disposal Area

Monitoring System Annual Data Report - 1978, Supplement E,

Brenton Reef Disposal Site" Naval Underwater Systems Center

for U.S. Army Corps of Engineers, New England Division, 424

Trapelo Road, Waltham, MA 02254.

3

6

311
4."

AN OVERVIEW OF A DREDGING DEMONSTRATION IN

CONTAMINATED MATERIAL, JAMES RIVER, VIRGINIA

R. E. Hudson

District Engineer, Norfolk District

R. G. Vann

Chief, Dredging Management Braich, Norfolk District

Department of the Army

Corps of Engineers, Korfolk District

803 Front Street

"Norfolk, Virginia 23510

ABSTRACT

The James River, Virginia, is a tributar,- of the

Chesapeake Bay polluted with the toxic pesticide

Kepone. The Norfolk District of the Corps of Engineers accomplished maintenance dredging operations

"within the polluted portion of the James River

channel during fiscal year 1982. As part of the

channel maintenance, the District conducted a demonstration of a dredging method designed to contain

and temove a polluted layer of sediment with a minimum of resuspension. The method involved modifying

and fitting an existing dustpan suction head to a

contractor's cutterhead dredge. The dredge was then

operated using an anchoring and maneuvering wire

arrangement that enabled precise positioning of

"the suction head within the specified layer of polluted sediment. Monitoring of operating paraseters

onhoard the dredge, of resuspension at the suction

head, and of water quality around the dredge and

disposal area was accomplished with aropropriate

equipment. The dredge was also operazed in the

conventional cutterhead configuration for compArison with the duhtpan arrangement. The data

gathered during this demonttration project permitted evaluation of the dredgting and disposal

methods utilized, and will he useful in planning

future projects in the James River and other

sites involving polluted dredged material.

, II I II4II I I
INTRODUCTION

The Norfolk District is located in Virginia, and includes the lower half of the Chesapeake Bay with its a-any tributaries, as well as a portion of the

Atlantic Coast. In serving the nation, the maintenance of navigation channels

and harbors is one of the most important missions. We have over 60 authorized

Snavigation projects that are active, totaling over 700 miles (1100 km) of 5 waterway. Depths in these channels vary from 4 feet (1.2 m) in the smallest,

to 45 feet (13.7 m) in the largest harbor projects.

Our deepest projects serve the vital ports of the Hampton Roads area,

where eventual deepening to 55 feet (16.8 m) is planned. Hampton Roads also

provides deep-water access to the James River, one of our more important

tributaries.

BACXGROUN"I

The James River (Figure 1) generally flows easterly, from the Allegheny

Mountains of western Virginia, to its mouth at Hampton Roads and into the

Chesapeake Bay. Between the City of Richmond and the mouth, a distance of . 90 miles (145 km), the James is tidal aind navigable. In this portion of the

river, a navigation channel 25 feet (7.6 m) deep is maintained to serve the

ports of Richmond and Hopewell, and the industries between these cities. These

industries and port activities depend on the James River Channel for the

economical transport of many commodities and raw materials. As is the case

on many of the world's waterways, local industries have created pollution. In

particular, the Allied Chemical Corporation, at plants in the vicinity of

* Hopewell, Virginia, was responsible for the release of Kepone into the James

"" River systm. Between 1967 and 1975 it is estimated that as much as 65,000 - pounds (30,000 kg) of the highly toxic chemical was discharged into the James

River basin.

~to

lof

Figure 1. Location of James River, Virginia

313
Following discovery of the extent of Kepone pollution, and formation of

4. State and Federal task forces, the U. S. Environmental Protection Agency (EPA)

conducted the Kepone Mitigation Feasibility Study. As part of this effort,

the Norfolk District was requested to evaluate alternatives for the removal

of Kepone-contaminated sediments, and to investigate potential dredging technology and methods to control resuspension and secondary pollution. During

this mitigation study, a delegation from EPA and the Norfolk District visited

Japan to observe specialized methods of handling toxic sediments. The group

was favorably impressed with the Oozer Dredge because of its alleged ability

* to achieve a high solids-to-water ratio and minimize resuspension. As a

result of the Japan visit, the Norfolk District recomended that a demonstraS- tion project be conducted on the James River to evaluate the Oozer Dredge in

comparison with a conventional cutter suction dredge. The basis for the

recowmendation was that there would be a need to know the best method of

removing pollutant "hot spots," whether consisting of Kepone in the James

River or toxics in other areas of the country, if the Corrs were assigned

3 ,a cleanup mission.

The recommendation to conduct a demonstration project was made to higher

authority in early 1979, and resulted in much discussion among dredging experts

both within and outside the Corps. Info-mally it was suggested that a dustpan

dredge, appropriately modified, could perform as well as the Oozer Dredge in

* removing polluted sediments. It was further suggested that parts from retired

Corps dustpan dredges', if available, could be adapted to cutterhead dredge

*. plant. As a result of these discussions, an engineering consultant with

,. Amalgamated Dredge Design, Incorporated, presented a proposal to the Corps.

He recommended that an existing dustpan suction head and ladder, if available

from a retired dredge in the St. Louis District, be modified and fitted to a

3 contractor's cutter suction dredge. The effectiveness of this arrangement

* for dredging polluted sediment would then be tested and compared to the

conventional cutterhead arrangement. The dredging would be accomplished as

part of the maintenance of the James River Channel. This proposal was the

basis for the dredging demonstration project in the James River.

S.DREDGING METHODS

Since most persons in the dredging business, and related activities and

industries, are familiar with the various types of dredging equipment, detailed descriptions of the cutterhead and dustpan dredges and their operation

will not be covered here. It is important, though, to show some of the

* differences between the two methods.

Cutter Suction Dredge

The James River has been economically mair.'ained for decades by contractors with cutterhead plant. The conventional cutter suction dredge would

* appear to be well suited for removal of the contaminated material of the

James.

The two stern spuds of the dredge, often termed the digging spud and

walking spud, provide firm anchorage in the channel bottom. By rotating on

the digging spud while making radial cuts across the channel, the dredge is

314

S I m m m m m m m m m m m m m m m
able to move accurately over the specified dredging area. Dredging depth and

"* output can also be accurately controlled. Furthermore, cutter suction dredges

can discharge the material over long distances, which is a distinct advantage

"if polluted material is to be deposited in a distant containment site.

The cutterhead dredge does have apparent disadvantages for dredging the

contaminated James River sediments. The rotating cutter can cause resuspension

of material at the head, particularly in the silty-clay of the James. The

action of the cutter also adds water to the material in excess of the in-place

water content, increasing disposal area needs if a containment site were required. Because of the geometry of the cutterhead dredging pattern, overlap of

the dredge cuts cannot be avoided. These overlaps result in additional, unwanted dilution water.

"Dustpan Dredge

, The dustpan type dredge was developed for use in maintaining the lower

Missouri and Mississippi River channels, and can achieve high outputs in

granular materials. While the dustpan is a hydraulic dredging method, as is

the cutterhead, it differs in how it maneuvers and excavates.

While operating, the dustpan faces into the swift river current and is

* held on station by two crossing headwires, anchored well upstream. The wide

"but shallow opening of the dustpan suction head is advanced straight ahead

into the shoal and makes long cuts by hauling in the two headwires. The advantage of this method in removing polluted material is the straight line

advance, permitting a constant width of cut. The dustpan dredge can also

accurately control the depth cf dredging. I

The dustpan dredge has disadvantages for working in the James River. The

dustpan head has a number of water jets at the mouthpiece which fluidize the

granular material of the Mississippi River bed, permitting flow into the suction head. These jets enable high outputs of granular material, but would

"cause unwanted resuspension and dilution of the fine-grained sediments of the

James. This soft but more cohesive material may also cause choking in the

• "dustpan head, and may possibly spill over and around the head. Finally,

-' additional anchor lines would be needed in the James River, where currents

* change direction with the tide, versus the steady current of the Mississippi.

The Problem of Total Containment

To effectively remove a layer of contaminated sediment involves a concept

)ur consultants termed "total containment." This is more than simply dredging

-L Oe sediment. The specified layer should be removed at maximum density to

"" lessen disposal problems. Resuspension should be minimized to lessen water

- quality problems and the amount of contamination left behind. Ideally, no

* more and no less than the desired volume of sediment would be removed. It is

apparent that accurate placement of the dredging equipment in the material is

a nectssity.

In the James River estuary, the sediments forming shoals in the navigation

channel are primarily silts and clays, with relatively low densities and high

3

• J' 313

S
6

moisture contents. While this material is "easy digging" for a typical cutterhead dredge, it makes the problem of total containment more difficult.

Our consultants proposed, in essence, to combine some of the advantages

of the cutterhead and dustpan methods of dredging, and eliminate some of their

inherent drawbacks. The resulting dredge system would be further improved

with an anchoring and maneuvering arrangement adapted from gold dredging techniques, and with advanced electronic positioning equipment.

MODIFICATION O" DUSTPAN

SUCTION HEAD AND LADDER

Entry Design

. The suction heat on an existing Corps dustpan dredge was equipped with

water jets along the top of the mouthpiece, and digging teeth on'the bottom,

to enhance the flow of granular material. These features are undesirable

for dredging of contaminated silt, and removal of them was recommended.

Our consultants proposed fitting the dustpan (Figure 2) with a newly

fabricated mouthpiece, to present a hydraulically "clean" opening to the

material, without trash bars or grates. Still, the material had to overcome

the entry losses of the flat rectangular mouthpiece. A rollover plate., shaped

like a bulldozer blade, was recommended to accomplish this, by building up an

K artificial head of material at the top edge of the entrance.

The layer of material created above the head entrance would have a tendency to spill over the sides, leaving some of the specified material undredged. To prevent this, wing plates, attached to either side of the dustpan,

and a splitter plate, attached in the center, were proposed. These plates were

designed to provide some stability for the head as it advanced, and also to

prevent the entry of dilution water at the sides.

Dredging Ladder

Modification to the existing dustpan ladder was advised for two reasons.

First, the ladder required an extension to enable dredging at the greater

"depths of the James River. And second, this ladder needed to be modified to

fit the well and trunnions of a contractor's cutter suction dredge.

ANCHORING AND MANEUVERING THE DREDGE

"As well as mouthpiece design, total containment depends on the ability to

accurately place and maneuver the suction head with the dredging area. This

is dependent on the method chosen for wiring and anchoring the dredge.

4 The method proposed for the James River may appear unorthodox, but was

based to some extent on mining dredging, where accurate movement and positioning is also needed. Under the proposed anchoring and maneuvering arrangement

(Figure 3), the dredge would set up perpendicular to the channel center line,

and make cuts across the channel between a head wire and a stern wire. The

dredge would be held on station not by a spud, but by calibrated radial wires

I

316.

I
Suc T 10*4PLT

IPIPING WN

PLT

IFigure 2. Modified Dustpan Head

a a W 

II

II

Figure 3. Wire Arrangement
anchored on the center line at a common point several hundred feet to the side.

On the opposite side, our consultants recommended a wire anchored again on the

channel center line, to keep the radial wires under constant tension and to

enable smooth arcs across the channel.

To accurately move the dredge from one station to the next, the consultants proposed taking in an amount on the radial wires equivalent to the width

of the dustpan head, and adjusting the tension wire. The resulting dredged

pattern would be a series of smooth arcs across the channel. Overlap of the

cuts would be minimal because of the length of the radius.

INSTRUMENTATION

The instrumentation recommended by our consultants fell into two broad

categories: equipment for positioning and tracking the movement of the dredge

head, and equipment for measuring and assessing the performance of the dredging

system.

The first group included an electronic positioning system comprised of a

three range navigation system, data processor, plotter, left/right indicator,

and input/output terminal; and a ladder depth indicator with radio-transmitted

tide correction. The navigation system would aid in accurate horizontal positioning and tracking of the dredge, while the ladder depth indicator would

permit precise vertical placement of the dredge head.

The second group included transmitters and electronic indicators for pump

vacuum and pressure and for discharge line velocity and density; a production

calcul'ator to measure output by integrating density and velocity; and a system

for sampling and measuring turbidity around the dredge head. Our consultants

also recommended the recording of other parameters that could be read on

existing gauges, such as engine speed and engine temperature.

PROJECT IMPLEMENTATION

Environmental Coordination

Since discovery of the Kepone problem in 1975,. all dredging projects

within the lower James River basin have required special consideration. At

first it was believed that disposal in upland containment areas would be the

best disposition for Kepone-laden dredged material. State and Federal environmental agencies eventually adopted a policy that recommended open ,ater disposal whenever feasible. Several reasons accounted for this change. Since

historically the method of overboard disposal was used for most of the James

River maintenance dredging, upland sites were generally not available near

the Kepone contamination. Officials could not justify the tremendous expense

of developing and using new upland sites for maintenance dredging requirements,

which account for but a small percentage of the Kepone present in the river.

Fears that Kepone deposited in upland sites would contaminate groundwater and

be introduced to the upland food chain provided further impetu toward a policy

of open water disposal.

During early 1981 the Corps presented the James River Dredging

1 18
Demonstration to State and Federal environmental officials. The project was

proposed not as a "cleanup" effort, since open water disposal would be used,

but rather as a demonstration of a potential cleanup technique. The agencies

endorsed the project concept, some enthusiastically, and during the spring

and summer of 1981, they met with the Corps to work out final de.ails. Extensive water quality monitoring by both the State and the Corps was an important

part of the pl~n.

Design Phase

A contract for architect-engineer services was awarded to Amalgamated

Dredge Design, Incorporated, to prepare plans for the project and to act as

chief consultants. The plans primarily involved design of modifications to

the dustpan head and ladder, modifications to an existing cutter suction

dredge, choice of onboard dredge instrumentation, and a program for carrying

out the dredging tests.

Visits to the retired Corps Dredge KENNEDY were made to determine which

dustpan parts could be made available for the project. The St. Louis District

assisted by removing and delivering the specified parts to Norfolk, including

the dustpan head and dredging ladder.

The designs could not be final until after it was known which cutter

suction dredge would be used. The Corps received bids from four firms for

lease of a dredge, and the low bidder, Norfolk Dredging Company, was awarded

the dredging contract. The 18-inch ( 4 50-mm) cutter suction dredge ESSEX was

designated.

During the design phase we also initiated procurement of the recommended

instrumentation packages. For horizontal positioning, the contractor ordered

"a Tellurometer model MRD-I three range navigation system and Digital Design &

Development model PSS-I data processing system. For vertical positioning of

the dredge head, an Observator model KK-22 ladder depth indicator with tide

correction was ordered. The dredge process instrumentation included IHC

Holland transmitters and indicators for pressure, vacuum, velocity, and

density, with a production calculator.

Maintenance Dredging

Restoration of the James River Channel would involve the removal of about

a million cubic yards (756,000 cu m). We realized tLat the dredging demonstration effort could accomplish only a portion of this. Because of time limitations, the bulk of the dredging would need to be done conventionally. And

conventional dredging could be accomplished before completion of plans for the

demonstration and actual modification of the dredge, while waiting for delivery

of essential instrumentation.

During November 1981 Norfolk Dredging Company removed 613,500 cubic yards

(470,000 cu m) from the channel in the vicinity of Jamestown Island, using the

ESSEX. The Corps and the State Water Control Board monitored water quality

during this dredging, and found that Kepone levels remained within safe

limits, both in the water and in shellfish. Dissolved Kepone did not exceed

319
9 parts per trillion, well within the water quality guideline of 15 parts per

trillion.

Modification of Dredge

With final modification plans, Norfolk Dredging Company put the ESSEX into

Colonna'E Shipyard in February 1982 (Figure 4). The dustpan parts were

reassembled, and the new mouthpiece installed. A ter extension of the ladder

and modification of the suction piping, the dustpan was fitted in the well in

place of the existing cutterhead ladder. Meanwhile, the anchor wire arrangement was altered to permit the new mode of operat on.

A gantry on the dustpan head was installed to) support turbidity sampling

tubes. These tubes fed through a manifold to a piump for filling the turbidity

test tank on the starboard deck. In the lever room, technicians began setting

up instrumentation for positioning and output measurement.

Dustpan Dredging Tests

During April 1982, Colonna's Shipyard completed work on the ESSEX. We

still larked some of the instrumentation being shipped from Europe, but the

decision was made to mobilize and start testing the dustpan configuration.

The final items to complete the instrumentation package were the velocity and

density transmitters, which were received, instalJed, then made operational

during the first week of May by the suppliers service engineer. The dustpan

dredging tests were conducted by Norfolk Dredging Company with the continuous

support and advice of the engineers with Amalgamated Dredge Design, during

the period April 13 through May 15, 1982. Approximately 69,000 cubic yards

(53,000 cu m) was removed from the channel using the dustpan configuration and

operating only during a 10-hour daylight period.

Cutterhead Dredging and Tests

Norfolk Dredging Company towed the ESSEX to their yard after completion

of the dustpan tests, and replaced the dustpan head and ladder with the original cutterhead and ladder. The dredge wiring and anchor systems were also

rearranged For cutterhead operation. Upon completion of this restoration work,

the ESSEX w..s again mobilized to the James River, this time for testing of the

cutterhead mode of operation and removal of the remaining shoals. Our consultants again took readings of turbidity around the head, and of vacuum, pressure, velocity, and density. The dredge contractor operated the ESSEX on a

normal 24-hour day, with the exception of the 10-hour daylight period for

testing and monitoring. Approximately 387,000 cubic yards. (296,000 cu m) was

removed between May 25 and June 15, 1982, with the dredge operating as a

conventional cutterhead.

Water Quality Monitoring

During the periods of test dredging, both dusltpan and cutterhead, we

again conducted an extensive water quality monitoring program. Kepone and

turbidity levels stayed within acceptable limits, and the effects of the

disposal operation were confined to the open water disposal area. The dredging

320

/
I Figure 4. Dredge in Shipyard

tests provided an opportunity for the Waterways Experiment Station (WES) to

conduct independent studies of the effects of the dustpan and cutterhead configurations on suspended solids levels. The State Water Control Board did not

monitor during the dredging operations, but did sample to determine Kepone

concentrations in the disposal areas after completion of dredging.

RESULTS OF DEMONSTRATION

Dustpan Tests

Norfolk Dredging Compar s crew in cooperation with Amalgamated Dredge

Design handled the setup and operation of the ESSEX in the dustpan mode

efficiently and professionally. Crew training in this unfamiliar arrangement

took place onsite during the f:::st ten days and included maneuvering tests.

The wiring and anchoring arrar. w rnt satisfactorily kept the dredge on station,

once the crew became proficienL and problems were worked out. These problems

included anchor and winch brake slippage, and the' stern wire catching on the

pontoon line.

The success of the anchoring arrangement enabled accurate placement of the

head from one cut across the channel to the next. This was desirable in

trying to achieve "total containment" of polluted material. Our consultants

believe the overlap between cuts was kept within acceptable limits of 3 feet

(I m) as compared to the width of the head of 28 feet (8.5 m).

Even with accurate pacement, the dustpan head was not able to contain the

material as well as we had hoped. At the slowest speed of advance (7.7 feet

or 2.3 m per minute) with a 9-inch-deep cut (23 cm) some material spilled

over the head, creating turbidity. Our consultants believe this problem resulted from the poor hydraulic radius of the dustpan head and resistance to

flow of the silty-clay. These conditions also contributed to occasional

choking of the head. Average production was 300 cubic yards (230 cu m) per

hour of operation.

321
-. -- - - - - - - - - - - - - -

Cutterhead Tests

Withthe ESSEX refitted to operate in the cutterhead mode, the contractorp.

completed the dredging tests without significant problems.

Turbidity readings from sampling points at the suction head showed the

cutter created significantly less resuspension than the dustpan. WES data

confirmed this, showing a cutterhead plume in the channel averaging 10 mg

per liter less than the dustpan plume. Density and output were more consistent

and higher in the cutter mode than in the dustpan mode.

Throughout the final phase of cutterhead dredging, overall production was

high, averaging more than 700 cubic yards (535 cu m) per hour. The contractor

and consultant both, attribute this to the relatively ideal conditions: soft

material, good weather, and a pumping distance to the disposal area of only

2,000 feet (600 m). We believe this is also an indication of the "can-do"

attitude of the contractor, and the dredging industry in general, as well as

the efficiency of the conventional cutterhead d edge.

Comparison of Dustpan and Cutterhead

With any comparison of the two modes, we must keep in mind that the dustpan was modified in an attempt to contain polluted sediment, and that maximizing production during this phase was not a primary goal. This is in contrast

to the cutterhead phase, where the dredge was operated efficiently and

conventionally.

It was no surprise, then, that the cutterhe'd mode achieved higher production. During hours of operation (10 hours per day with dustpan, 24 hours

with cutter) the cutter suction mode averagcd more than double the production

of the dustpan, on an hourly basis. Contrary to our anticipations, though,

the dustpan also did not perform as well as the cutterhead in limiting resuspension at the head. Both our consultants and the Waterways Experiment Station

observed higher levels of suspended material at the dustpan than at the -

cutterheod.

Water Quality Monitoring

The Norfolk District obtained valuable water quality data during each

phase of the James River dredging. A team consisting of survey technicians,

boat operator, scientists, and engineers sampled water for various parameters

around both the dredge and the discharge point. The use of a survey vessel

with electronic positioning enabled the samples to be taken at predetermined,

known locations.

Our monitoring plan concentrated on Kepone and turbidity. Neither of

these parameters increased significantly above background in the water

column around the dredge head, for either dredging method. The situation

differed at the disposal area. While levels of turbidity and suspended

solids in this area were similar, but slightly higher during the cutter mode,

the dissolved Kepone levels for the cutterhead averaged more than three times

"the levels during the dustpan mode (11.7 versus 3.2 parts per trillion). This

is perhaps explained by the fact that the cutterhead moved more than five

times the amount of material moved by the dustpan, during more or less equal

periods on the calendar. At the disposal site, Kepone and turbidity levels

322

J
remained within acceptable limits, and the elevation of these levels was short

term and confined to the designated disposal area.

During the first phase of maintenance dredging in November 1981, the

State Water Control Board conducted a study of Kepone levels in clams held

within the disposal area. The Board's study concluded that Kepone Ln the

shellfish rose slightly as a result of the disposal operation, but not enough

to be of concern. Rather than test shellfish again during the dredging tests,

the Water Board chose to sample surface sediments in the disposal areas. This

study showed that sediment Kepone levels were higher after the cutterhead phase

than the dustpan phase. This may be due again to the vast differences in

quantities deposited during the two phases.

EFFECTIVENESS OF INSTRUMENTATION

Prior to this project we had no experience with the instrumentation used

on the James River. The dredging demonstration has provided the opporLunity

to gain experience with and judge the effectiveness of the instrumentation

packages.

Electronic Positioning System

The three-range electronic navigation system, coupled with data processing

equipment and plotter, proved valuable in delineating the work area and the

path of the dredge within accuracy of,+ one meter. Dredge operators in the

lever room could monitor the dredge hed location with respect to the channel

using either the plotter or a left/right indicator.

As well as providing accurate horizontal positioning of the suction head,

the system could also indicate when the anchoring and maneuvering wire arrangement was functioning improperly. Slippage from the desired location would

show up as a deviation on the plotter as it traced the dredge head path.

The electronic positioning system was not free of problems. Early in

the testing program, our technicians determined that the system was malfunctioning, and a service engineer-was called in for repair. We have learned

that effective use of a sophisticated system such as this requires highly

trained people for operation, monitoring, and routine maintenance of the

equipment.

Dredging Ladder Depth Indicator

The ladder depth indicating system proved valuable to Lhe dredge operator

for accurate vertical positioning of the dredge head. The system measured the

angle of the ladder, translated this into a depth, and corrected for the

height of the tide. This freed dredge personnel from periodically reading the

tide at a distant location and calculating the required depth.

One problem with the depth indicator surfaced shortly after start-up.

The system was not properly correcting for the radio tide signal. The supplier's service engineer promptly adjusted the system, and for the remainder

of the project no other problems occurred. Again, this indicates the need

323
to have trained technical people available.

Dredge Production Instrumentation

Discharge pipeline velocity, density, and output readings were provided

in the level room and were some of the more valuable data obtained during the

project. To the dredge operator, this additional information was of little

value, since he could operate as efficiently as possible using pressure,

vacuum, and engine speed gauges. However, to our consuitants, readings of

velocity, density, and output were essential in evaluating the dustpan and

cutter modes of dredging.

After calibration and start-up of the production instrumentation, the

system proved steady and reliable. Our problems with this equipment were in

procurement. For any instrumentation manufactured overseas, and particularly

for the density transmitter with its nuclear source, we recommend long lead

times to allow for procurement approval and licensing.

SUMMARY AND CONCLUSIONS

Our dredge contractor and engineering consultants did a commendable job

in starting up and executing the dredging demonstration in the James River.

In the dustpan mode the wiring and anchoring arrangement worked well and provided the needed accuracy. In terms of "total containment" the dustpan head

did not perform as well as we hoped. Our consultants suggest that with the

dustpan's wide- flat opening and poor hydraulic radius, improvement may be obtained by some means of vibration or cutting action. This would reduce the

resistance to flow which caused spilling over the top and sides of the head.

The consultants also suggest that a different suction head design, such as a

Fruehling type head, may be better in dredging contaminated silty-clay.

The selected instrumentation proved effective both in positioning

accuracy and in evaluating dredge performance. Electronic equipment for

horizontal and vertical positioning of the dredge head was more valuable to

the dredge operators than was the production instrumentation. Management

personnel of the dredging firm believe the package providing output, velocity,

and density readings could be an effective tool for evaluating dredge performance problems. For sophisticated electronic equipment of any type, it is

highly desirable to have well-trained technicians available, and contracts for

service and mai.tenance are recommended.

The water quality studies conducted during the demonstration project

showed that dredging in the James River does not create problems with Kepone

resuspension or turbidity. The C(rps and the State of Virginia have already

used our documented monitoring results in evaluating and permitting other

key dredging projects in the James that would otherwise have not been possible.

The District is also using the information to develop a long-term disposal

solution for a badly shoaled military port facility at Fort Eustis.

Overboard disposal proved to be economical and without serious environmental effects. The total project cost, including the additional costs for

dredging tests and water quality monitoring, worked out to about $3.00 per

324
- cubic yard removed. Alternative plans such as upland disposal range as high

as $5 to $10 per cubic yard. We believe that dredging managers, engineers,

* environmental scientists, and other individuals, who have a responsibility for

channel dredging or removal of contaminated material, can benefit from the

various findings of this project.

BIBLIOGRAPHY

1. U.S. Environmental Protection Agency. 'Mitigation Feasibility for the

Kepone Contamiaated! Hopewell James River Basin Areas, Appendix B." Office of

Water and HazardouslMaterials, Criteria and Standards Division, Washington,

D. C. June 1978.

"2. Pezza, D.A. and Buck, R.L. "James River Maintenance Dredging Demonstration

Project, Goose Hilliand Dancing Point-Swann Point Project Channels, Virginia,

Subsurface Investigation." U.S. Army Engineer District, Norfolk. January 1981.

3. Haller, D.L. "Demonstration of Advanced Dredging Technology, Dredging

Contaminated Material (Kepone), James River, Virginia." Proceedings of the

6th U.S./Japan Experts Meeting on Management of Bottom Sediments Containing

Toxic Substances, UIS. Army Corps of Engineers Water Resources Support Center.

March 1982.

0

0
V

FIELD DREDGING TEST OF SOFT MUD LAYER BY

A FRONT-OPEN TYPE DRAG HEAD

. Yoshitugu Iris

"Second District Port Construction Bureau

SUMMARY

This paper describes the result of a field dredging test carried out as

part of a study of a method of effective removal and disposal of bottom

sediments in a vast closed water area such as Tokyo Bay.

We manufactured a new type drag head that can dredge soft mud, dredging

thinly and widely, in high density. We equipped a trailing hopper, suction

dredge (hopper capacity of 4000 m 3) with this new drag head and field tested

off Chiba in Tokyo Bay. Good results were obtained.

The 5th District Port Construction Bureau manufactured a second drag head

of the same type and equipped the trailing hopper suction dredge "Seiryu

Maru' with it and field tested in Ise and Mikawa Bays.

FIELD DREDGING TEST (I) AT CHIBA PORT

Based on the results of model tests conducted in 1977 and 1978, we manufactured a tull-sized drag head, equipped a trailing hopper suction dredge

with this head, and performed a field test.

The four factors to be investigated included:

* Dredging characteristics of the drag head.

" Effects of mixing blades, a stabilizer, and a protector.

' Control of dredging depth of the drag head.

" Occurrence of muddiness.

Drpdge

The dredge used in this test was a trailing hopper suction dredge

"Tokushun Maru No. 1". Main specifications of "Tokushun Maru No. 1" are shown

in Table I; general arrargement is shown in Figuire 1.

Test Location

Location of the field test is shown in Figure 2. The dredging area wa.

200 m x 1000 m. Depth in th's area is 13 m on the average as shown in Figure 3, and an incline Is oily 0.5 0/00 in the direction of the dredging l!ne.

326

S. ..
Drag Head

"An outline oi the drag head used in this test is shown in Figure 4. The

of the drag head Sfront was a rectangle, breadth B = 2.3 m, height H 0.5 m,

and area A - 1.15 L 2. A screen for prevention of refuse was fixed to the

front, and detachable mixing blades 440 mm in diameter were installed in the

'-7.... -

S ' " - ...

l - •-7.-r--r "" ',' . '. - . S.

Figure 1. General arrangement

Table 1. Main specifications of "Tokushun Maru No. I"

Ov'erail length 113.35 m speed

pp* 106.00 m maximum

Shre.idth 19.60 m cruising

,epth 9.00 m dredging

,.ra u'n4ht t).90 M main engine 470G PS x 450 rpm x 2

:r-,s tMnn,igk- 1.21 I. t drag arm side drag type 800 mm x 2

&,d w• .: r c',ipwi'r. a•3 t dredging pump 3 3/h

:,; e r • c1 i ' 8(),)n n/hr x It m x 170 rpm x 2

d )z x: ,, M swel I crpensator x 2

• ~r ¢,,r", ,,r ,'I rott ioned n - prit at the end of this piper.

• . . .. . .

S .," , .. • . .÷. .
-. . __ _ _ _ _ _ _ _ _ _ _ _ _ _ __ _ _ _ _ _ _

Test Area - /

4 I , ." Ciba City

LZI

Test Area -

4 "- \ in..t~6it .sm Ee~I Ligh Beac 

•.C I B 8 ! ,"n . /

jD' C 271 I.

3 A D 'IN

Figure 2. Location of the test

-100

333 3 1

-13

0 100 200 200 400 S00 600 70C to0 900 1000 (M)

Figure 3. Depth in the rest area

328

Si!II
nixing unit \

I, -d

ord tLin for rubbis 'h

Figure 4. Drag head

drag head. A detachable stabilizer, breadth - 2.3 m and length = 1.1 m, and

four sets of detectors for soft mud surface of seabed were installed on the

forefront of the head. Four detachable plates 400 mm x 300 mm were attached

on the sole of the head.

Ahen the shape of the head was selected, the area and the ratio of breadth

and height were the principal factors. Values of these factors were based on

the results obtained by experiments with models, and we had to decide the area

of the front of the head first. For this decision, the nondimensional parameter Y 0 was an important factor. It was supposed that blockade of the

suction pump occurred when T 0 as nearly 0.9. Therefore, T0 =0.8 was se- 0 0

lected as the design value. Other parameters were set up as shown in Table 2.

Table 2. Variables

Variable To VS Qo

Base value 0.8 3 kt 8,000 m3 /hr

329
The area of the front of the head could then be calculated from

A H Yo Qo/Vs ()

therefore

2 A 1.15 (m2)

Since the radio of breadth to height does not severely affect the performance of dredging, the height was designed to correspond to the thickness of

the Hedoro sediment H = 0.5 m (but this was the condition in 1979, and now we

"* are going to study the technique of the thinner dredging). Consequently,

breadth B was 2.3 m and the ratio of breadth to height was 4.6.

*. Figure 5 is an outline of the mixing blades. These blades were driven by

the hydraulic motor; maximum power of the motor was 86.5 Ps/300 rpm and was

driven by the hydraulic unit on board. A hydraulic circuit is shQwn in Figure 6.

S~Figure 5. Mixing blades (rotor)

.. Investigation of Hedoro at the Location of the Test

[i•] The investigation is outlined as follows:

o• The area of the investigation....shown in Figure 3.

o Items of the test....1 release test: cyanogen, cadmium,

• sexivalent chrome, total mercury,

lead, arsenic, organic phosphorus,

PCB

S~2 mud quality: PCB, total mercury

.-. physical properties: specific gravity,

-' grading, water content, consistency

" ~(liquid limit, plastic limit), vane "rtest (undisturbed sample, disturbed

* sample)

Results of the investigation are as follows:

1 Release test ..... all items were nondetectable (ND) as shown in

Table 3.

330

led reiogai hshrs

n I IPCB
Table 3. Results of release test

Limit of

No. 1 No. Sapl 2 No.opDtcto 3 No. 

Alkyl mercury compound ND ND ND ND 0.003

Mercury and mercury compound ND ND ND ND 0.003

Cadmium and cadmium compound ND ND ND ND 0.1

Lead and lead compound ND ND ND ND I

Organic phosphorus compound ND ND ND ND 1

Sexivalent chrome compound ND ND ND ND 0.5

Arsenic compound ND ND ND ND 0.5

Cyanide compound ND ND ND ND I

PCB ND ND ND ND 0.003

llydriiwj:ic Uri g

0 n2

Gd riue49A. - ZZA

nae ru0menm

elMti WA~a uie1 (Dt:mc luc a

U ~ ~ ~ ~ hyr:i ~ ~ I I~ 1 ree (D49acwuau 

3 'ste coupline 10 suctlongvif . c, u~e ap

filter ~ 114"fle ~ ~ I hroec ~ F 

ule n amec I'dgob nalmenm

eletri Ftgure 6.~c if Hydauic crcluicet~
2 Mud quality ..... shown in Table 4.

Table 4. Results of mud quality test

Limit of

Sample No. Detection

No. 1 No. 2 No. 3 No. 4 ppm

Mercury and mercury compound 1.10 0.96 0.93 0.79 0.01

PCB 0.11 0.07 0.07 0.07 0.01

3 Physical proper'ies ..... samples of tests were collected from the

upper layer, middle layer, and lower

layer of seven column samples; results of

the tests are shown in Table 5.

Table 5. Physical properties

Upper Layer Middle Layer Lowec Laver

Cobble (Z) 0.0 0.0 0.0

Sand (%) 11.2 4.3 3.0

Silt (Z) 51.3 56.5 60.9

Clay (Z) 37.5 39.2 36.1

Liquid limit (%) 88.4 81.6 80.2

Plastic limit (Z) 53.2 46.7 45.1

Plasticity index 35.4 34.9 35.1 .I

Specific gravity 2.664 2.709 2.733

Water content (Z) 340.7 197.2 182.4

Vane test undisturbed 9.07 x 10-4 12.26 x 10-4 17.00 x 10-4

disturbed 4.42 x 10-4 4.88 x 10-4 6.64 x 10-4

Means of Test

Parameters of this test are as follows:

Velocity of the ship (V ) S

o Rate of flow of the suction pump (Q)

332
o Thickness of dredging (d H)

o Existence of the mixing blades

oExistence of the stabilizer

Cases of this test are shown in Table 6. Items of measurement are shown

Table 6. Cases of Experiment

ve loc ity rate of flow T~h ickness Tmixing h1rides stabi-

(kt) (rm'/l1 !of dredg. 1 (rpm) Iizeri

Case 1 Nr . note

v2 V2 Q V34 Q1 Q2 X1 X Y1 Y2 Y3 ZI 721

10,000 800M I 1,, 0 ",go 3''"'

1110~~~V 0 * l ' V:2.Okt

C12 0 0 0 V2 :2.5k t

. IV4:3.5k t

72 6 0 0 0 j stabilIizer

C3 'r ' '0 10 ix

0 0C40' blades

ll~P 0 0' 0 0(150rpm)

'13! 1'10 0 - 'c1

1500 '0 0~ blades

16 0' ' 0o 0 Q 0 (300rpL I

! 0 ' Cci ,5 0 + stabi IiL

'CS~1 8mI ~ ixing

'2' 00'blades

91 1 0 0 10 0 thicknss of

0 I 1- , dredging

23 0 , 1.5

24 0 .

2' Q-1 thicknss of

C7% 0 0 p dredging 1.5,

27 rmixing

28 blades

29 00 r0I

CS ?0 00 C ~ 0 0 rate.offlo

'0 '0 o

33 '. . 0 ' . n rate of f1'I

"9 0 1~ ~~0 00vf

5 o 0 thicknss of

3F -''J redgiing 1.5

333
, / /

in Table 7. Sounding was carried out at two places, one at the bridge (No. 18

in Table 7) used for measurement of the depth of dredging, and the other at

the upper deck used for measurement of the trace of dredging. Water sampling

pumps were fixed at the middle of the drag arm and at the drag head, one set

of the submergible pumps at every two positions. Water was pumped up to the

upper deck continuously and sampled properly. Measuring locations are shown

in Figure 7 (numbers in Figure 7 correspond with those in Table 7).

Table 7. Items of measurement

No.* Items Means Location Note

1 Draught Draught meter Bridge Continuously

2 Water level of hopper Float Hopper At intervals of

1 minute

3 Depth of the drag Pressure transducer Upper deck Continuously

head

4 Pressure of the swell Pressure gauge Bridge At intervals of

compensator 15 seconds

5 Displacement of the Potentic meter Upper deck Continuously

swell compensator

6 Rolling of the vessel Rolling meter Bridge Continuously

7 Rate of flow Electro-magnetic Bridge Continuously

flow meter

8 Density Isotope density Bridge Continuously

meter

9 Suction pressurd Differential pres- Pump room Continuously

sure transducer

10 Discharge pressure Pressure tranducer Pump room Continuously

11 Number of Tachograph Bridge At intervals of

revolutions 15 seconds

12 Electric current Ampere-meter Bridge At intervals of

15 seconds

13 Density at trough Water bottle Upper deck Once per one run

14 Turbidity iround the Submergible pump Upper deck Twice per one run

drag head

15 Turbidity around the Submergible pump Upper deck Twice per one run

drag arm

16 Turbidity in background Turbidimeter Upper deck Continuously

17 Position of the vessel Electric position- Bridge Continuously

ing equipment

18 Sounding (i) Echo sounder Bridge

19 Sounding (2) Echo sounder Upper deck 200 kHz

20 Sampling of Hedcro Bottom sampler Hopper Once per one run

21 Hedoro layer Detector Upper deck Continuously

* Numbers correspond to Figure 7.

334
Fiue7 oc oso mesuemnt

troue hh caseg

°13 17,'

"mnecass o hoppert

24.8 • 3..

T2h etim oic 4 ea fu r i

o .e.dr.gin tie...aou 25. mi run

105.

Figure 7. Locations of measurement

The term of tests was from I October 1979 to 6 October 1979. Vhen considering a time schedule, we calculated the time required for each case onr the basis of the volume of dredging soil, and considered a time schedule to

manage cases of tests properly."-

The time required per one case (which equals four runs) is •

"° Net dredging time ... about 25 min/4 runs ]]

"o Turning time .......... about 45 min/3 turns. i

°Sailing time .......... distance 10 km, velocity 10 kt, therefore, .-

about 65 min/round trip

Dumping time .......... about 25 min

The sum total is 160 min.

Consequently, the time schedule was planned as in Table 8 (1),

and the time schedule was carried out as in Table 8 (2).

Results of Test

Marine and Meteorological Conditions

Before and after this field test, Tokyo Bay was struck by a typhoon,

but it was calm during the test. Therefore, the test was conducted without

hindrance. Meteorological conditions are shown in Thble 9.Y

335
00

- m

~14

aAKF __

- _ _ _ _ _ _ 0_

_5i~I

- _____ ____336
Table 9. Meteorological conditions

Wind Atmospheric Temperature

Date Time Direction m/s Weather Pressure (mb) (°C)

8:00 SE 5 clear 992.0 28.0

10.1 12:00 SE 5 clear 995.0 28.0

16:00 SE 5 clear 997.5 27.0

8:00 ENE 7 cloudy 1005.0 24.0

10.2 12:00 ENE 9 rainy 1007.5 22.0

16:00 ENE 8 cloudy 1008.0 22.0

8:00 NNW 10 rainy 1008.5 18.5

10.3 12:00 N 5 cloudy 1007.0 19.5

16:00 NNE 8 cloudy 1005.5 21.0

8:00 N 4 cloudy 1001.5 20.0

10.4 12:00 N 3 cloudy 998.5 23.5

16:00 N 2 cloudy 996.5 23.5

8:00 N 5 cloudy 1001.0 20.0

10.5 12:00 NNE 5 cloudy 1002.0 23.0

16:00 NE 7 cloudy 1002.0 25.0

8:00 NE 4 rainy 1007.0 18.0

10.6 12:00 NNW 8 rainy 1009.0 17.5

Bottom Soil Condition

Soil conditions were investigated before the field test and the dredged

soil was sampled from the hopper of the dredge during the field test. A

grain-size distribution curve made from this sample is shown in Figure 8;

the specific gravity of the soil particles was 2.63, a flow factor curve

is shown in Figure 9.

Results of Field Dredging Test

Results of the test are shown in Table 10. These values are mean values

during one case of the test. The contents of each data are as follows.

Furrows and velocity of the dredge. Furrows during dredging tests were

obtained from electric positioning equipment and are shown in Figure 16.

Velocity of the dredge, which was obtained through calculating positions of

the dredge, had a mean value for 10 sec.

Depth and thickness of dredging. Thickness of dredging was obtained from

a difference between depth of the head and water depth. Water depth was

measured by an echo sounder and depth of the drag head was measured by a pressure gauge on top of the drag head.

3

337
100 ___ - - __ Li..

60 -I

40 - .. --.. 

I --- ,.,, -,. ___t .,,, ,. .• :,

a4si' F NAME. r oe 2 ,4 6 e, 2o' 4 6 S 1o, 4 6 5, 102-

am.i. size (/pso

Figure 8. Grain-size distribution

.200-

SG 

so" .. --- "10"0

lo 444

30-

: °~i...

a

10, 4, - °1•.:

e3 -

to.. o.

Figure 9. Flcw factor

338

3 !
4

Table 10. Results

operating condition n ccitin'ious recnrd loading volt me a Test 11• -- --- r------- - -- -- - . .... - dredging

vel. dl 1 U 0 'f O rate of density specific dredging time contin, watter "coti

Qin/ fIlo C v gravity volume data I dl daft

rn/s (Wn n?/Il1 UO rn /I 1 (1) ne/lI (min.) IQ (o?') I (d) TU

TI - I 1.4 0.36 9 103 0.374 7903 5.3 1. HO 417 9 1272 l139 140

2 1.29 0.10 9545 0.107 9561 1.5 i049 141 7 1193 ;119 125

3 1.41 0.32 9943 0.376 8744 5.9 1.120 516 4 648 '7) 71

T 2- 0.83 0.30 9060 0.231 8258 4.2 1.092 344 6 892 0 97

2 1.25 0.56 9372 0. 55 1 77801 6.3 1.125 487 6 866 6

3 1.55 0.28 9%94 0.3bb 6984 9.6 1.178 667 6 774 81 69

"1' T3- 1 h 1.66 0.23 9031 0.315 7675 6.4 1.12 - 49-4 5 716 7,o 761 -, CO 

. 1.03 0.38 93105 0.348 8047 5.6 1.115 449 5 7,13 7 81:

3 1.54 0.28 9588 0.368 8140 6.5 1.130 531 5 744 8. 9U-.

T4-1 1.03 0.44 90,50 0 414 8M14 4.3 1.095 3 5 765 8 -5 83

2 2.01 0.23 93.38 0.413 8494 5.9 1.119 499 77 T73 86

3 1.56 0.23 96326 0,o09 8264 6.0 1.121 492 5 771 86 85

4 1.66 0.33 9934 0.._9 _..3 1.0 391 3 524 3.,5

"" 5- 1 1.39 0.66 9017 0.640 4669 12.5 1.225 582 4 403 445 47'

2 1.66 0.38 9185 0.561 5842 9.3 1.174 542 4 485 416 55.

3 1.33 0.58 9391 0.587 7845 7.3 1.142 570 4 600 53 67!

4 1.82 0.46 95W 0M27 5956 11.9 1.216 709 6 662 6)36 79r

T6- 1 1.13 0.64 9046 0.518 7050 8.8 1.166 621 648 71V 74f

2 1.85 0.52 9276 0.827 4663 12.3 1.223 574 4 410 389 48.

3 1.51 0.18 9430 0.6.35 4388 13.6 1.243 596 5 467 4;8 bbi

_. __4 1.89 0.61 9602 0.815 4831 13.3 1.238 642 6 5_3 6111 68

'1'7 1 1.12 0.34 9491 0.337 8722 4.0 1.M 3.18 4 652 ... 70

2 1.15 0.32 9731 " 317 8X37 6.3 1.127 530 4 638 6,34 71

3 1.55 0.30 9947 0.387 "1403 9.1 1-172 676 4 556 5ig 64:

4 1.92 0.38 10168 (1-%59 6572 10.1 1.187 662 7 8%2 8 1

T 8-1 1.07 0.41 9ý50 1 0.380 8254 6.7' 1.132 549 4 5219 646 70

2 1.65 0.23 9-4 1" 0.323 8855 5.2 1.109 461 4 603 UV 72

3 1.69 0.28 10000 0.390 8?,') 7.0 1.138 610 5 811 817 9!,

4 1.85 0.24 10298 0.35? 9206 6.2 1.125 574 4 702 &)b5 78,

• 9-- 1 1.08 0.64 9510 0.471 7885 8.7 r.,64 G8.4 5 7"1 '53

2 '.88 0.53 9741 0.7n9 4474 1.7 I.211 657 6 528 ,•D, i 61'

3 1.11 0.61 1 OW0 0.459 8098 9.7 1.181 788 5 "463 114 8'ý

.0 104 .7) 55785 MI 13.3 1.2-39 742 75fA 731 91

TI0-- 1 1.29 0.30 9186 0.342 81037 4.1 1-0,1 357 4 7 6.25 70

2 0.80 0).28 9731 0.191 9157 .1.8 1. 085 .44 4 f() 7

3 2.04 0.29 9976 0 497 8475 7.3 1.142 18 4 13,2 7%

4 1.80 0.4.11 10202 0.637 6370 12.3 1.23 7 85 7143 718

'I'lI-1 I 1.35 0.24 84r,3 0.319 733fi 5.0 1. IT ) 11A 5 131" 71 71 4 2 1.73 0.28 ,Y96 0.A,5 6815 7.3 1.12 2 5 73

3 1.314 0.23 8946 0.287 7172 8.8 1.11 1,12 5 ,6 6714 7

"4 121.78 0.19) 9)100 0.3)2 1')'151 9.1 k12 617 5 W7) Im 1,!

112 -1 0.95 0.,H 8 IF) 1 0.I'( 1,4f,2 8.8 1. I f 5 k5 6 7,3 74 8

2 1.0f) 0 V)1 S720 0.489) 558 1 11.7 1.213 r'12 6 Fr) 1, 16 7

3 1.31 0.5 8956 0 0.I,04 5109 11,6 1.211 (28 6 610 M 1 71

4 1.80) 0.49 9190 0.791 41S85 11.1 1.234 K.17 8 742 lio)

['.1'13 1 .5q 0.52 TI.7'; 0.75 - 1 f1) 91 11.5 LM21 '1% 5 013 F51 7

, 2 2.03 0.57 1)7071 0. (,5 401•, ,61 1.21.3 (,52 "H2 81

I...i

'! /

.4] , l )(, ( [• [, . • ( • 1 1 ) , ( l i

r
4

Table 10. Results

ccntinpmos record loading volume loading weight spific .. .. . dredging -- gra-ity # S-M draught depth rate of density specific dredging time contin. water Conti$. water ot slumry level

/ flow C v gravity volume data level data level in hopper

4 7903 5.3 1.110 417 9 1272 1309 1405 1444 1.104 0.8.4 M7 19

im/Il (•) d/Ili (age.) 1U(d U e) TG o U To. r. (in) (n) (in)

7 9561 1.5 1.049 141 7 1193 1219 1250 1324 1.047 1.11 5.53 14.3

6 8744 5.9 1.120 516 4 648 210 718 512 1.108 1.29 6.12 14.5

I 8258 4.2 1.092 .344 6 892 910 970 970 1.011 1.94 4.64 15.1

.1 7780 6.3 1.125 487 6 859 967 982 1.117 .954 5.19 14.8 ".6 6984 9.6 1.178 667 6 774 811 896 921 IAW 1.95 5.76 15.0

• 5 7675 6.4 1.123 494 5 716 761 8W 806 1.116 0.60 4.57 13.8

8 8047 5.5 1.115 449 5 743 707 838 866 1.1 A 0.57 5.03 13.7

8140 6.5 1.130 531 5 744 M 83 917 I.AW 0.55 5.55 13.8

4 8:%4 4.3 1.095 T)3 5 765 845 82 85 1.00 0.81 4.59 14.1

3 8494 5.9 1.119 499 5 7 7A 8uu 873 1.10? 0.89 5.08 14.2

9 824 6.0 1.121 492 5 771 826 857 891 1.114 3.03 5.61 14.5

8 90 4.3 1.094 193 3 524 375 546 1.00 1.21 6.02 14.4

0 4669 12.5 1.225 582 4 403 445 475 479 1.178 1.71 4.48 15.0 41 5842 9.3 1.174 542 4 485 476 552 509 1.139 1.83 4.77 15.0

7 7845 7.3 1.142 570 4 60 83 675 68 I.i2 i.91 5.14 15.2 "7 5956 11.9 1.216 70' 6 02 F 72 834 .195 1.96 5.56 15.3

8 70'50 8.8 1166 621 5 , 48 716 746 731 1.152 2.05 4.58 15.4

7 493 12.3 1.223 574 41 3V) 484 513 I. 1.183 2.00 4.92 15.1

5 4388 13.6 1.243 59S 5 407 413 56 524 1.201 I,9. 5.24 15.4

434 13.3 1.238 642 6 573 611 919 745 1.203. 1 5 5.2 15.0

8722 4.0 .1 .9 348 4 652 ;)q 4 7,11 1.060 0.83 4.51 14.3

7 8194 6.3 1.121 'A0 4 We 634 711 641 1.114 0.7. 4.^2 14.2 7 7403 9.1 1.172 671, 4 556 538 W 665 1.152 0.'3 5.2 14 0

9 6572 10.1 .18 IJ62 J 7 862 &12 1006 9W 1.7135 U.- 5.78.. 9

J3 8855 5.2 1.132 59 4 6Z V6 703 615 1.116 0.78 4 53 14.1 13 88,5 5.2 1 I. 109 0;I .C,,,I CO 727 78 1.09? 0.85 l!.-5 WC 1 0 8700 7.0 1.138 610 5 'llI 817 910 936 1.123 or.97 5.43 34.1 2 9206 6., 129 574 4 )2 655 780 82 1.111 3.05 S.92

7885 8 1. R (,14 5 7 21 - .. .814 1.151 1.67 4. % 1.31

9 4174 14.7 1.l4 N I 6 .. W8 !y. 646 61l I.23 1.79 5.M) 11.9

9 8 7 1.11 +98 5 1 34 848 847 1.164 3. 5.43 Il.') 5578 3.3 1 742 7 7-6 731 911 920 1.20 2.03 5.93 14.1

2 43 .1.3 1.091 357 4 l FA a5 1701 j713 1.085 0.97 4.49 414

")157 3.8 1. 85 14 4 $A 1 bl 734 737 .077 0 .q1 4.92 WI3. 9l415 73 1.142 ,18 4 f))2 b I)J -,i 732 1.127 0.85 .3.1 I.

;,.370 12.3 1.223 785 6 743 718 887 9.32 1.3I4 0.77 5.81 n.8

lT,• 5.0 1.106 674. 11 7-4 73.1 I8 0.68 4.53 13.309 .7.9 7 I.I 5 I " 6.1 7 77"4 1.132 9.72 4ci 31 1, 7 1-,2 8.9 1.610 F, 12 5 b75 6:4 772 814 3.142 0.75 Fl; , ,3 I I i.2 H ,5 1 f5J7 W645 75.3 71A 1.145 0.U85 .. 1 3

""3,I, R. 15 .5 6 72! 7q) 8V0 812 1.148 1.34Z j.56 is

,1 11.7 1.13 .2 ,52 1 6 651 616 7fiq 746 1.180 1.35 .i,2 34'

4 54(n 33.6 1.211 Q28 6 (.'30 612 746 W 1.15 ,2.U 'A.45 15.0

7 48') 13.1 1.2.34 KrI 8 742 716 897 913 1.V06 2.11 5.81 !,",.,

! 33'+ 1.5 j. 3.210 . 1 .5i; r,3 3*0 . 7414 7L"<J 1 .f'76 I L 41 5.. I.2.3 4.49I 34I

4: 0 .. l 13 .4 , 7.h 8 3.9 8 2 5 1 .2 W I . I. , 41 tv 1 .

UIAJd, J JAO.3 J . UJJil 1NJ4Nu 
Ida

:4-

in 10 , 1- Wln s t

3m..... -iz[ ,-----"- -4

* .l,.g -'-----it{--

:, zzL zzb K--iFigure, 10. Furrows

After dredging started, thickness of dredging increased with Increased

water depth. Therefore, in this test we took the changes in draught and the

pressure of a soft mud seabed surface into account, and operated the draghead-winch in a manner to maintain the planned thickness of dredging.

Discharge of the suction pump at water supply. Actual head of a pump

changes with a change in draught; this change is accompanied by a discharge of

the suction pump. Results of the discharge of the suctionpump measured at

the field test are shown in Figure 11.

Densitv and rate of flow. Density of slurry in !he pipe was measured by

"he Isottpe type density meter; rate of flow of slurry in the pipe was measured by the electromagnetic flow meter. These results are shown in Figure 12.

Analysis of the Results

Density and Decline of Discharge

i)ensirv and discharge flow rate are inversely proportional to each other

,and aire determined by soil condition, characteristics of the pump, and state

o: dredging. Fig-.,re 13 shows the tendency of a decline of a discharge flow

l rate with an increase of dens.tv. In the California type drag head used for

sand. s,•il, this decline of discharge has a tendency to be linear, and does

not decline hastilv as in the field test. This results from the additional

reI tance cai,;,ed by an increase of density when a dra? head is buried in soft

mud 3,; in this test. From Figure 13, an equation with respect to a decline of

discharge becomes

1.55

Q /Q - 1 - 10.3 C (2)

341
p.-

I.

0 -

0 A "i~ 0

I 11-i 'mh.'

Figure 11. Discharge of the suction pump

5. "T 9-2 dH=O.SY(m) VS188m/s)

20 14

F 3. 4, I t&. I z. 

Figure 12. Continuous data

I" -
0.8

0.6

0.4 9

0.2

00.05 0.10 0.15 0.20

CV

O h tFigure 13. Rate of flow and density

On the other hand, quantity of solids dredged per unit time is written as

Gs = C I (3)

using Eq. 2, Eq. 3 is expressed as

G s/Qo C v(1-10.3 Cv (4)

and then Eq. 4 is shown in Figure 14. From this equation, quantity of solids

dredged per unit time has the maximum value when density is 12.1%, and

quantity of solids dredged per unit time cannot be expected to increase over

this density. This trend is confirmed in Figures 15 and 16.

0. 05

0

0 .1 0.2

CV,

Figure 14. C and quantity of solids dredged per unit time

343
C r

'-I

-'- I r f

.V11I. U - .. t/ I "' L

i !," i"- il I 1I

J -f/ J I I i

0 2 3 4

v ( win

Figure 15. Density and quantity of solids

dredged per unit time

0.2 10 9-

-cv y177 -- I _ _I jl Arm I A .. . 3 4 - - T t I'

°" _,' -- I I .* II

'IiPiii I .L.!1 I I __

0. ____ A tI K I1- I I 1-1 I

SI "1li I

Figure 16. Density and quantity of solids

dredged per unit time

344
Conditions of Operation and Density

In the model experiments C showed a comparatively large value at the v

smaller T' and an increase in C became less at the larger Y But it 0 V 0

was found in this experiment that C increased linearly up to T 0 0.8 as V 0

shown in Figure 17.

0.1i

black dM•0.5

Figure 17. C and f V 0

This is expressed by the following equation:

0 .17 'Y (5)

V 0

At a Hedoro water content (depth of 30 cm), apparent density becomes

Ca (Wn/lO0) y Cvy +C (6)

and substituting into Eq. 6:

W = 220%, y = 2.63, y = 1.025

n s w

then C becomes, a

C = 6.64 C (7) a v

Therefore, we obtain the following equation by substituting Eq. 5 into

Eq. 7:

C = 1.13 $' (7') a oS

Figure 18 shows a relation between C and ' . This expresses that Hedoro was

dredged a o at fairly high density when q was large.

0 0

345 "
0.0

0.4 - 0

0-RAS

0 --

0.2

S black d"•.-)

0 0.2 0.4 j 0.6 0.8 1.0

*0

Figure 18. C and Y a o

Effect of Mixing Blades and Horizontal Stabilizer

Both the mixing blades and the horizontal stabilizer increased the added

resistance when the drag head was not buried, but when it was buried mixing

blades caused a decrease in resistance. ýThis suggests that mixing blades can

improve the blockage condition of the drag head.

It is important to note that liquidity of Hedoro in this test area was

too low to have a flow factor but the blockage, which occurred in the model

experiments, did not occur. Because the'blockage did not occur, the ratio of

the cross-sectional area of the suction pipe of the drag arm to that of the

inlet of the drag head was remarkably improved. It is important that the

proportion of a geometrical shape of a drag head be well balanced.

Change of Quantity of Solids Dredged

per Unit Time and Remnant of Dredging Sohl

The quantity of solids dredged per unit time is fixed by the combination

of a decrease of the rate of flow and increase of density; therefore, Eq. 3 is

rewritten as

Q,'

C s =C V .- Q" .Q 0

and substituting Eq. 2 and Eq. 5 into this equation, we obtain

C /Q 0.17 (1 1o - 0.661 'Y 1.55 (8)

5 0 0 0

346ý
I

Therefore, quantity of solids dredged per unit time has the maximum at

W = 0.714. This result indicates that production of the dredge is optimized

at this point.

Another factor is the amount of material presented to the drag head that 4is not removed. Now taking the ratio of quantity of Hedoro forcibly sent into

the head to quantity of Hedoro actually dredged, we make it li/ as

I/E (Q IN * CB)/ (Cv Qm) (9)

From W = 220%, then C3 = 0.15, and arranging experimental data, we obtain

Figure 19. Judging from this figure, we find that the drag head cannot remove

all the material presented to it when C is greater than 0.4. It is necessary for us to investigate how this remanant affects the appearance of

muddiness.

2.0

0 -

A R

1.5 •

aka~

'~~~T ... - -

0 0.2 0.4 0.6 0.8 1.0

Figure 19. & and T0

Depth Control of Dredging

Depth of dredging is usually controlled by a swell compensator. The drag

head follows the sea bottom by controlling air pressure of the swell compensator,

using bearing capacity. But we could not expect bearing capacity of Hedoro in

this test and many unknown factors existed such as buoyancy and bearing

capacity acti:ng upon the bottom plate of the drag head when the drag head

,.as buried, etc. Therefore, we decided to control the depth of dredging by

winch operation instead of swell compensator.

Tn this test, we first measured the water depth with the echo sounder;

second, we set up the pobition of the drag head by adding thickness of dredging

to the denth; and, third, we wound and rewound the winch properly by considering

cor tinucusr mr.asuring data on dredging conditions (for example, water depth,

draught, density, and detector for soft mud seabed surface). These results are

shown in Figure 20. "he example without winding the winch is shown in Figure 21, when the drag head was buried.

347
I IT9-2

E 1.0

0.5

0.

0

0.5

.tu• 2 II -.-

0 3 4 5 67 Time (mi..)

Figure 20. Thickness of dredging

This operating method is practical where the sea bottom has gentle undulations as in this test, but when the sea bottom has ragged undulations, it is

very difficult to follow the sea bottom by hand operation of the winch. Therefore, It is necessary to establish a technique for automatic operation.

1.5 TE 1 _____ 1

1.0

S0

C.. m; .

Figure 21. Thickness of dredging, buried drag head

Turbidity Caused by Dredging

All samples taken by the submergible pump at the middle of the drag arm had

suspended solids (SS) values under 15 mg/i and turbidity was nonexistent.

Samples taken by the submergible pump at the drag head had SS values mostly

under 10 ng/., but a few of the samples showed considerably higher values.

Table 11 shows SS density values recorded over 30 mg/i.

348
5

Table 11. Examples of turbidity

SS Sampling Time Up or Winching Time dH V s

Test No. (mg/L) M S Down M S (m) (kt)

T 5-4 130 1 00 + 1 00 0.46. 3.63

T 6-2 600 3 00 t 3 00 0.52 3.59

T 6-3 2500 2 30 t 2 30 0.48 2.93

T 6-4 8400 2 30 t 2 30 0.61 3.67

4600 1 00 ....

T 9-2 6300 3 00 . 2 40 0.53 3.65

320 5 00 t 5 20

T 9-4 300 2 30 ± 2 30 0.50 3.40

T12-4 40-60 ...... 0.49 3.53

3400 2 30 t 2 30

T13-2 1300 4 30 t 5 00 0.58 3.94

From Table 11 it can be said that:

a. Very high SS occurrences coincided with operation of the winch.

b. High SS occurred only when the thickness of dredging was over 0.- m

(the drag head was buried) and speed of the ship was high.

Judging from these trends, it is possible that, when the dredging parameter

0 is large, the remnant of dredging soil occurs in front of the drag head, 0

rises up on the upper surface of the drag head, and is diffused by the winding

operation of the winch.

Detector for Soft Mud Seabed Surface

In this test, we manufactured detectors for soft mud seabed surface by

measuring attenuation of an ultrasonic wave. Four pairs of transducers were

used, of which one pair consisted of a transmitter and a receiving oscillator

1 m distant from each other. Attenuation of an ultrasonic wave between

a transmitter and a receiving oscillator was continuously measured, and from

the data of attenuation we detected the existence of soft mud. A receiving

level does not actually change linearly between two neighboring pairs, but

we simplified as in Figure 22 to calculate linearly. Figure 23 shows the com--

parison between the result of the above calculation and that of the depth of

349
VD//

bI

A0 ,

A I/

0 t time.

b-klb (when. t-.) •

Figure 22. Method of calculation

the drag head. From these results, the detector showed the wrong: information

when T was large (velocity of the ship had an important effect in this case), 0 because a soft mud surface in front of the drag head was built from the unentrained soil and turbidity appeared. But when the ship (dredge) sailed

slowly, the detector showed the comparatively correct information.

4 •Remaining Tasks

Dredging Performance Near Blockage Boundary

We could not obtain the characteristics near the blockage boundary from

the condition of this test. So we could not confirm whether or not the

characteristics obtained from the model experiments could be applied to a

full-sized drag head. Therefore, an experiment in Hedoro of low water content

is needed.

State of Turbidity

We sampled water by a submergible pump installed upon the drag head in

order to measure turbidity around the drag head. This revealed the basic

characteristics of turbidity, but it was impossible to analyze the distribution of sediment resuspension and the mechanism of occuirrence of turbidity

quantitatively. Therefore, it is necessary to conduct experiments using many

water sampling pumps and TV cameras, etc., to analyze and observe the state of

turbidity.

350

/N.
- --. 3.3

I I 1B1 Detector

By Detector-ofDa a'

8vDepth -t 4-- DLpth o rgHa

2 1 3 4 5

0 Lj 4 2 2 1tiw I i.~ I

(a)(C)

J J -1 I I I II I I

By netector ~jDetector BVll~ 

--- ~-I* BY-e- -- B---t~

3 2 12 L 44 

ti~ ~Ln I tin. I i I

Figure 23. Depth of the drag head

351
* 1⁄2j

FIELD DREDGING TEST (II) AT NAGOYA PORT

A field dredging test at Nagoya Port by the trailing hopper suction dredge

"Seiryu Maru" was carried out in February 1981, following the field dredging

test (1) in 1979.

The' factors investigated in this test were fundamentally the same as

that of the test in 1979, but since we manufactured a new drag head for

"Seiryu 4aru" use, the factors are arranged as follows:

O Characteristics of dredging by "Seiryu Maru"

0 Characteristics of dredging of Hedoro in low water content

Dredge

The dredge used in this test was the trailing hopper suction dredge

"Seiryu Maru"; main specifications are shown in Table 12.

Table 12. Main specifications of "Seiryu Maru"

Overall length 94.9 m Maximum speed 13.3 kt

Lp.p. 88.0 m Dredging speed 6.33 kt

Breadth 16.0 m Main engine 3000PS x 400 rpm x 2

Depth 7.2 m Dredging pump 4100m-/hr x 17 m x 450KW x 2

Draught 5.6 Drag arm 620 mmd side drag type

Gross tonnage 3526 GT Swell compensator

Dead weight capacity 3202 t Bow thruster c.p. propeller

Hopper capacity 1754 m 300KW x t Max. depth of dredging 22 m

Test Location

Location of this field test is shown in Figure 24. The dredging area was

200 m x 780 m.

I

The sea bottom in this area was sounded before dredging. A part of the

depth is shown in Figure 25. The sea bottom in this area is considerably

uneven due to previous dredging.

I

352 .

I
,-" I Fier Na

.. L.:: . . . .

,, ý- e

est rea- - kinou Pier

to& I ,C-.0

7 -- -O

0'

S•

I -';' "i

i•Figure 24. Location of the test'

•"..''. Dr ag~ Head

S~An outline of the drag head used in this test is shown in Figure 26. It

-- . 'WE s a front open type with the front of the drag head shaped In a rectangle, breadth B - 1.8 m, height H - 0.4 m. Fundamentally, this is the same structure

i Bottom Soil1 Conditions

I-• --.- The fluidity of the bottom was so low that the soil could not flow out by

@ its o,4n dea-.' load at the flow test; i.e., the flow factor was infinite.

. '-, 

°

Age353

Isafotoe yewt h rn fteda edsae narcage
6 F

;T _ F__ T Y*-l 7

-• _

__.... ..__ ... 1• --.L..-

/.

Figure 25. Sounding data

Figure 26. Drag head

354
Grain-size distribution of the soil, which was sampled from the inside

of the hopper after dredging, is shown in Figure 27. The specific gravity of

soil particles was 2.60.

li00 F l mark ts

50o - I. T i -3LE sg

F0 F~i 4'j•- i l , ii, *,/ T •--. 2.58 8 S.. ",a T- t 5 14

""0 1 T 1I 1-3 IT t

*::Io -1 I•i~

_= 0 F.s•_• i = IS: ! I{ . __ !....! _ _........ i...i.i. ttt

- t-1 .0 T - t 102

cla I ~'es&- ~ar, sa.Jrcbln e rm

I 1T05 2 1J74 Z 56 t

Figure 27. Grain-size distribution

Means of Test

Table 13 shc'~.. items of measurement. A detector for soft mud seabed

surface was set in front of the drag head, a signal was amplified in the relay

roost, near the draz arm tr-unn~ion, and output was simultaneously recorded by the

: data recorder in the bridge. Two water sampling pumps were fixed at the drag

head, and one was at the middle of the drag arm. Measuringl locations are

j shown in Figure 28.

tResults and Anaivsi,3 of Test

t s Jiesl 1 

In this test, the seabed was so uneven that it was very difficult to set

up the depth of the drag head. We calculated the posit or of the drag head

."ror, the po~sition and direction of the ship, and obtained the depth of the

seabe-d by collatring the position of the drag head with a sounding chart. Where

the denth of the ;eab~ed, obtait'ed as stated above, is SR and the depth of

2DR

the sole of the drag head is SH , the relatilcn to the thickness of dredging

sewn in Figure uis and is written: d9 

dH ThSH -DSR (10)

To oebain the characteristics of tTse dredgin pump installed in "Seiryu

•aru," we conducted a water msupplying test and measured rate of water flow

dat The relatr ion between and the distance from the water surface to the

pshrp So o ) Figure s shown in .(38. Table 14 shows the results o. this test.

rp

355
"Table 13. Items of measurement

No.* Items Location Means Note

I Depth of the drag head Drag head Pressure transducer

2 Suction pressure Inlet of pump Pressure transducer

3 Discharge pressure Outlet of pump Pressure transducer Continuously

4 Rolling of the vessel Upper deck Differential pres- sure transducer

5 Hedoro layer Inlet of head Detector

• 6 Rate of flow Outlet of pump Electromagnetic

flow meter Continuously

7 Density Outlet of pump Density meter

8 Turbidity around head Upon head Submergible pump

9 Turbidity around head Upon head Submergible pump Several times

10 Turbidity in Drag arm per one run Submergible pump background 4 11 Hedoro sampling Open trough Sampling valve

12 Water level of hopper Hopper Float Several times

per one run 1-3 Hedoro sampling Hopper Ekman barge

14 Draught Bridge Draught meter

15 Depth of drag head Bridge Air barge At intervals

of 30 seconds 16 Velocity of the vessel Bridge Doppler log

17 Position (Ra,Rb) Bridge Electric position- At intervals ing equipment of 10 seconds

18 Depth of dredging Bridge Echo sounder Continuously

19 Rate of flow and Bridge Electromagnetic At intervals density flow meter and of 30 seconds

density meter

20 Suction, discharge Bridge Bourdon pressure press gauge

21 Muddiness in test area Turbidimeter At intervals

of 10 minutes

22 Water sampling Craft Water sampler At intervals

of 60 minutes

N Numbers corresponds to Figure 28.

'56

I
Fiur 2. octinsofmesuemn

(:4

Figure 29. S DR' S DH and dH

357
(M I

0 00

Q* -- 419t5 -- 0+420~4

0 -- I

4x1O 3

606

4 I03 x 

....

3XO

3.2

D7p (-?

Figure 30. D r 'd G

r" .

Changes of Dredging Characteristics

Since the drag head could not follow the rolling s, bottom in this

test, the thickness of dredging changed on a large scale. Therefore, we

cannot discuss the average dredging characteristics. Instead, we can discuss

changes in the dredging characteristics.

An example of the relation between the sea bottom and the depth of the

drag head is shown in Figure 31. Generally, the drag head could maintain

stability while following the gentle unevenness of the sea bottom; however,

once the drag head got stuck in the mud of the sea bottom because of the

roughness of the bottom, it took a long time to return to the stable condition. This was especially true for low water content. T2-3 in Figure 31 is

an example of this phenomenon.

As for the relation between the control of the drag head and the bearing

capacity of the bottom sediments (Hedoro), in spite of setting the pressure of

the swell compensator for a maximum of 15 kg/cm2 and with Hedoro being comparatively hard, the swell compensator operated only under the condition of

the drag head getting into Hedoro of 60 - 70 cm. It is necessary to install

a suitable stabilizer (one which is suited to the bearing capacity of Hedoro),

and to control the depth of the drag head. When the water content is more

than 250 - 300%, the stabilizer, which is suited to the bearing capacity of

Hedoro, becomes an unrealistic size; in this case the drag head without a

stabilizer can obtain better results.

358
-.. _ I 00 0 Z 

___w __ ___ __ ___ c gK ";E; 

to a, m ~ m~ Lo

_ý: 0 =4- 0-0c

Iý ___ In - c -R -, 

g m0o 8;;J cn _ I~ mI 7

cnr- c, co c,. -o ~

C) ~c. 1 2, .C~~ Z. C'ý CSC' 

oo.D --. In cý In. -c-. IQC - c-r I I I " -- . 1 -C--

03 c ,ý cý , ,ýc *.ý I. . ..

w = cm a) 7rI c- u, gi 0 c

i c40 l0 7'C~ Il~ . - .C.~. 9- -

m____________ _____o___ c cý Z 6 Z. 7. _6___ Z 1 . I oc mm_

0 C> 0 000 0w 00 0 w m 10 

w~~~~~0 FF L9c oI 00 00)ý 00- I 7,2 c9 .7 7 0ý 10 ll 000c

I= Ll. c:,:! . . c .ý , . =

-~, rw ? rt~l. ~ 0C 0 L~n 11 (0- 104f4ffýlIfu

359
10

Ix I

---- S DR I 10

C 1.2 .3 4 ~ ~ 5

time (min.)

Figure 31. Sole of the drag head and sea bottom

The relations among thickness of dredging, density, and rate of flow are

shown in Figure 32. Since they are arranged by the mean value, data are considerably scattered about, but the trend coincides with the results obtained

before. To watch this as the relation to the dredging parameter, we obtain

Figure 33. From this figure, the dredging boundary of this test is the point

of Y - 0.6 - 0.65 , which is at a lower level than that of the 1979 test.

0

In the California type drag head, the drag head touched the sea bottom

widely and dredged soft mud which was diluted by surrounding water. The swell

compensator operated effectively, but the density showed a downward trend.

Detector for Soft Mud Seabed Surface

It was confirmed that the detector for soft mud seabed surface operated

effectively to grasp the relative relation between the drag head and the sea

bottom on dredging. But the detector sometimes stopped the function by

adherence of soft mud, so it is necessary to devise a method to avoid adherence

of soft mud.

Turbidit" Caused by Dredging

Since we had a lot of unentrained soil in this test, we saw a considerably high level of SS (suspended solids). Figure 34 shows the relation

between the thickness of dredging and turbidity. We could not obtain a

definite connection with the condition of dredging in this test.

FIELD DREDGING TEST (III) AT MIKAWA PORT

A field dredging test by "Seiryu Maru" was carried out at Mikawa Port,

following the FY 1980 test. In order to improve operational performance, we

360
a 02 knorj

rotor (mixing blades ) V:60r-,

L 

I

ix K 04 . 5 0 ' 0

IX i

g6 6

1 I 6 a a 8

•" , Io• 

~XA X

X 

"I

XX 0

14 • J{ 2, 5i d '1 • 3a s

Figure 32. Thickness of dredging, density, and rate of flow

361
N '/ with a rotor

CL I I /

0L d 

1.0

ad

d *'

II

Ai

6|

Q5 LO

Figure 33. Y' , rate of flow, and density

0e

362

-4o,
31000

02 fnoLs xZ$

.3

200o -A IS

x 0 0

1000

x

A

*0

x 0 00 x 0 A0

XI

0 I Of 01 x 0 0 0 0

a 1 0.2 (1 4 Ck5 CL6

d#4 ton

Figure 34. Thickness of dredging and turbidity

enlarged the stabilizer and reconstructed the drag head to control posture

of the drag head by varying the angle of dredging.

Improvement of the operational performance of the Hedoro dredging

system for practical use was the object of this test. The factors to be

investigated in this test are as follows:

Characteristics of dredging A Automatic motion by means of the stabilizer and the swvell compensator

o Relation between the posture of the drag head and the dredging

performance

Turbidity by dredging

Dredge

I

The dredge used in this test was the same trailing hopper suction

aredge "Seiryu Mari." Main specifications are shown in Table 12.

Test Location

Location of this field test is shown in Figure 35.

363
Nagoya

Vokkaichi Jinno Wharf S• I Test 4re L

konaae --

Taliara Wh r

Figure 35. Location of the test

-.-

Drag Head

An outline of the drag head used in this test is shown in Figure 36.

This drag head, which was manufactured by reconstructing the drag head used in

FY 1970, had the same rectangular shape of breadth, B = 1 8 m, and height,

H = 0.4 m.

Improvements of the drag head for this field test were as follows:

2 a. Installed a stabilizer of 7.0 m

b. Made the bending Fart of the drag head movable in order to control

the angle of dredging.

Bottom Soil Conditions

Locations and results of the soil test, which was carried out before the

dredging test, are shown in Figure 37 and Table 15. Grain-size distribution

of the soil, which was sampled from the inside of the hopper after dredging,

is shown in Figure 38. Specific gravity of soil particles was 2.58.

Means of Test

(tems of measurement are shown in Table 16, and locations of measurement

are shown in Figure 39.

364

q
p"r

FigureDra Drgaea36. 

- -detector .

j -.

- -- AC 'Oationfs a crzait-s

la:ara Whar'

1 4 samoling PoifL for the so tesst

Buoy 2

.30

0 00 430 100 400 TRUO'. 4j

Figure 37. Locations of the soil test

365

I
Table 15. Results of the soil test

Specific Sampling No. Depth (m) Gravity Water Content

u 0.1 - 0.3 2.609 271.3

No. 1 m 0.4 - 0.6 2.649 176.4

1 0.7 - 0.9 2.670 132.5

u 0.1 - 0.3 2.626 231.3

No. 2 m 0.4 - 0.6 2.664 199.8

1 0.7 - 0.9 2.674 185.9

u 0.1 - 0.3 2.682 200.1

No. 3 m 0.4 - 0.6 2.644 194.3

1 0.7 - 0.9 2.678 143.7

u 0.1 - 0.3 2.640 187.4

No. 4 m 0.4 - 0.6 2.664 154.7

1 0.7 - 0.9 2.663 127.3

I

u~upper layer

rn:middle layer

l:lower layer

366

S~i
IOC ZiiiIIILllifl[i i I I

100 1.i. I .II 111 .. I 1T; T _______ 111!11 _ Hil

v Iiii j l~T I I I Oll I I iI

0 1 t0 30 I I it H l

10 3 10-2 lo- 1 . 1 1 to 102

0001 QOOS 0074 0 42 2 5 20 7

Figure 38. Grain-size distribution

!19

FL \ r .a .

* F'igure 39. l~oca3tlons of measurement

I4-II I
STable 16. Items of measuremenc

No.* Items Location Moans Nore

I Depth of the drag head Drag head Pressure crOM6oaeucr Continuously

2 Hedoro layer Detector

3 Turbidity around drag head Submergible p Several times

per one rue

4 Depth of the new bo.tos Echo sounder Continuously

5 Depth of the middle of the drag Pressure transdurer Several times

rarm pet one run

6 Turbidity in the background Submergible pum Continuously

7 Depth of the end of the drag are Predsure transducer

8 Suction pressure of pump Inlet of pump

9 Discharge pressure os pump Outlet of pump

10 Rate of flow Electroeagnetic flow meter

MI Density Density meter

12 Hedoro sampling Open trough Sarpling valee Several times

per o.Ia rue

13 Water level of the hopper Hopper Float

14 Hedoro sampling £kmaa barge

15 Displacement of s*ell compensator Swell compensaror Potentiometer Continuously

16 Draught Bridge Draught meter At intervals

of 30 seconds

17 Depth of the drag head Air barge

IA Velocity of the ship Doppler log

19 Position (RaRh) Electric positiening equip.

20 Thickness of dredging Fcho sounder Continuously

21 Rate of flow density EloctrusAgnotie flow moetr At intervals of

4 density meter 10 seconds

22 Suction pressure. otc. Bourdon pressure gage

23 Turbidity in the ctst area Craft Tturbidlmoter 10 minutes

24 Water sampling in the test area Water samPler 6O minutes

Nojmieri crrr.pond to Figure 39.

, , II I II I II I I I I I I I I
Results and Analysis of Test

Marine and Meteorological Conditions

Meteorological conditions (Table 17), were generally good; marine conditions were also good.

Table 17. Meteorological conditions

Wind

Speed Temperature Humidity Atmospheric

Date Time Direction (m/s) Weather (C) (Z) Press, (mb)

8/24 12:00 E 3 Clear 26 58 1002

!

8/25 12:00 E 5 Cloudy 26 75 1010

8/26 12:00 SW 4 Cloudy 26 90 1005

8/29 12:00 SE 7 Cloudy 28 74 1004

8/28 12:00 W 3 Cloudy 24 82 1009

Results

The result of the water supplying test is shown in Figure 40. Table 18

lists all the results of this field dredging test. Since T-15 in Table 18 is

the result of the California type drag head and the bases are different,

analysis of the relation between T-15 and other cases is meaningless; therefore, we did not examine these results. Water content of the soil, which was

used in the analysis of the test data, is obtained from Table 15.

W = 220% n

This is the mean value of the water content of the soil at a depth of 0.2 m.

Dredging Characteristics

Dredging characteristics are determined by taking that of the drag head

without a itabilizer for the basis. A downward trend of the rate of flow

becomes Figure 41. This is express-I by the following empirical formula:

m/Qo I - 4.59 C1 .3v (11) m av

The broken line in Fig 're 41 expresses the data of the usual fine sand

dredging test. The rate of flow of this test drops well as compared with

36,9
4

- -. 00 0 '00 tt

f00 0 0- 00 c--0 --- 0 CCO

'I

- Cs- tflt- .r.r .r. CC4 0 - -CJ Cr-. -eCs 02' c-,e 00 i-,- Cs,- 0,45 -00 oc-

- .00 00 00 0 00 00 0 00 00 00 00 00 00 00

C C*

0 C,.. -U-- Cs- U*0 f9 f.OC 0

& C Of C0 f-f-. t.. f.C-, t..CJ C-OL. Ofl

_____________ ____________________________________________________________________________

-- -- - Cs - C.. Cs -- C'..-------C'..- Cr

- te, 0 - *.'t= *00 CJ f-Cs *flUS 4 . 2 -

* . Cs.C ?0 .45L5 3f---0CrC'4 f-as -2 0 CC 0- CS - Cs. - t.4 a.C.J -car C'JC'J C4 C.JC'.a C..C4 C4 C'4 C'.JtZ

- C'.. .c . -oa.z A &-o -s f C'.,-

- .. t:.C, Cs.

GD

Crf- 90 f-0 .aS 0 CS0Cs 0 fC

- .45-ffl0 C'.. -t4CSf4flCstOCs4ttfla.Z

00 00 00 0 00 00 0 00 00 00 00 00 00 00 00

__ _____________________

-Cs *)C

t 

0 0,tr. -- Cs 0- C- .. aC '*.2 OC.4 -,cc. Cs

0.45 0. -0 0.... 00 0.... 0-

- 00 0 00 0 00 00 0 00 00 00 00 00 00 00 00

- -.r C'-aCs .2 r2 00 0 Cs Cs 00 0 2Cs --

- - - - - CaCs f-.... ZCZ 0 C.5 f-r .2.2 .450 -C

C -*o Z CC-a f-0 0 Cr0 f- - .. .. C... .. o . .... C-.. -,C .45.45

- -. 45 rut -r - - r -, -. 45 .r .45 .fl.SC ens - ("5

- 0. CSJC'4 - fC:C.2 - rf- t3 45 CCtfl z. ,nr .. zr- a- 'us csc, --- z -c'a oat -.-- -tat 6... & ,-ca ..n

- -- rso---------------------00 0 -- C'C'* 00

C

-Cs0 0CC C-JO 0 f-ar---- Cs .4 k2.2 f .450 *0 0 Out CsC"5 ('JO

f-c-, c-a-. a-..- c.a a'CCS -f-a - C-JCC '5Cs: -- -- ('aCs C.JCs rrC ('JC'.J

0 00 OCr 0- ("5 Out 0- 00 Oft -45 OCr 0C400 OCr Outa.a 00 0.0 00 OCr pa...Or - 00 --

* Cs at 42 ..C: 2 - - 2' -, 2' tat Z 0 tat .2 .45 42 uS .2,45 az. attn an en at 0

____________________________________________________________________ _______________________________________________________________

... C4 ..CNJ C\J -C\. C'.J C.4 -

- a*.a Cs .45 az - - a-a r - Jat

- It - C-

- - - Cr CC 0 CC 0

7()
ttoi a rocor

-at.f.rna .'o, .lra .ead )

C

Figure 40. Water supplying test

rhat of the ti-ne sand dredging test. The following equation expresses the

quantity of solids dredged per un~it time:

C /Q =6.534 C 1 -4.59 C

1 (12)

To differentiate Equation 12, the quantity of solids dredged per unit time

becomes maximu~m at the density of 16.3Z. But the natural density of the soil

(Hedoro) in the seabed CB was only 15.3%, so the density did not increase to

the peak value, and the pump operated only at 60% of capacity.

The relation between the suction density and IF is shown in Figure 42.

'his figure shows that the density is low when di under 0.4 m and increases sceadily when d His over 0.4 M. An illustration which expresses

the model of this phenomenon is shown in Figure 43.

371
i'z" -.0 .. lj . o I i

i I

CC v

Figur 41i esty & aeoffo

o .I'I 3 rotor (vixin¢ o taoes ) .

* with~out a rotor|

~11C i

Figure 41 Density & rate of flow

I0

r11 I I b ,acG37

S I I I; I I __

J i~i iTLN!J T [7 _

i rt i ,

i ! i I • /t "'° • 'J i .-.

o I I x____ __________

- I - iI l 22 i Ii ___

]1F1 Tl i _____7K

FigureI 42. Density and 'o

372
II II

C, =Cb > >

I I -

C,,t d, d _>0.47a:

," o

/ • YI: ;'$'2

Cf

Figure 43. Model of the basic dredging characteristic

Installation of the stabilizer influenced the characteristics of dredging when the velocity of the ship V was over 3 knots. When the drag head S

was buried, the stabilizer clogged the flow route of Hedoro, but when the drag

head was not buried, water easily diluted Hedoro.

The ratio of dredged Hedoro RR is shown in Figure 44 and is expressed

as follows:

RR (Ca Qm)/(B dH VH) = £ (13)

,tthout a stabilizer - ith a stabilizer

~~1~' ov-. 2 knots

I.0 2.0 c .,4

1.0F 0 0

AI I ;, I I

01.0 0 1.0

Figure 44. 0 and RR

373
6

For a drag head without a stabilizer, RR is 0.6 - 1.0 and the difference by

the velocity of the ship is small. For a drag head with a stabilizer, the

trend of RR is similar to that of the head without a stabilizer when the

velocity of the ship is 2 - 2.5 knots. But when it is over 3 knots,. influence of the stabilizer is exerted and the dredging efficiency drops.

Effect of Stabilizer

The (horizontal) stabilizer influences the characteristics of dredging,

and many planning problems remain; however, the stabilizer complements the

function of the swell compensator.

Figure 45 shows the comparison of the thickness of dredging between the

case of using the drag head with a stabilizer and that of using the drag head

without a stabilizer. We can find that the thickness of dredging shows a

stable condition near 0.4 m when using the drag head with a stabilizer. An

effect of the stabilizer is influenced by the angle between the drag head and

the seabed (a). The reason is that a little change to the angle a changes the

lift operating upon the stabilizer, and the swell compensator can operate

effectively only when the lift operates upon the stabilizer. (This is because

the lift makes up for a deficiency of the load bearing capacity of Hedoto,

bottom sediments, and makes the good condition for the operation of the swell

compensator.)

with a stabiizer

without a stabilizer j ot a stabilizer & sole plates open

I'[M

'10

S- 10

0 ~(deg) 0__ 

Figure 45. Thickness of dredging

374{

I I I I
Detector for Soft Mud Seabed Surface

Your pairs of sensors were installed, but soft mud (Hedoro) adhered to

the sensors located above the inlet of the drag head; therefore, recovery of

the function of the sensor was sometimes delayed. The two pairs of sensors

located urder the upper plate of the inlet of the drag head operated without

problem. Patterns of the receiving level of thesc two pairs of sensors are

shown in Figure 46. Judging from this figure, these sensors are considerably

effective when the velocity of the ship is near 2 knots; but when-velocity

is over 3 knots, these sensors often indicate incorrect patterns.

0 50 no0 9 30 L00

4.. I

0 '+L___

sensor ." a

1 ______- S. -______

&. I /

VVs-' knot!:

Figure 46. Patterns of the receiving level

Turbidity

Turbidity appeared deeply and widely near the drag head, but we could

not link turbidity ,,ith the dredging conditions. Two kinds of turbidity

appeared near the drag head: one about 10 times as deep as turbidity of the

background and always in the stable dredging condition; and the other very

deep with turbidity of about 5000 mg/Z. The latter appeared due to soft mud,

which accumulated on the drag head, being washed-by water when the drag head

rcse up to the sea bottom after being buried. But this sort of turbidity

appeared only infrequentIy and hardly influenced the background.

375
Measures for Improvement

Effective Position of Horizontal Stabilizer

It is possible to follow the sea bottom by means of the horizontal

stabilizer and the swell compensator where a bearing capacity of soft mud

(Hedoro) is expected. The position of the stabilizer is important. It is

necessary that the stabilizer enable an easy lift and not obstruct the

inflow of Hedoro. The stabilizer should be installed a short distance behind

the inlet (front) of the drag head.

Dvtector for Soft Mud Seabed Surface

Since two pairs of sensors installed under the upper plate of the inlet

of the drag head operated acceptably well, it is reasonable to control the

drag head by a system which uses the signals of these sensors. But the

frontal projected area of these sensors needs to be reduced so as not to

obstruct the inflow of Hedoro.

CONCLUSIONS

Seven years have passed since we started this development. During these

seven years, we carried out four experiments with models and three field

dredging tests. A summary of these field tests is shown in Table 19. Circumstances of the test areas of these field tests are different from each

other, and the dredges "Tokushun Maru No. 1" and "Seiryu Maru" were used.

Therefore, we cannot discuss results of these tests from the same point of

view. We carried out these tests with the front open type drag head and the

trailing hopper suction dredge for removal of a large volume of Hedoro in a

large area and to protect cruising ships.

Through these tests, we developed the technology of the front open type

drag head. In order to make this technology of practical use, a few operational problems remain: improvement of the handling performance, and the -.

need for a means of positioning the ship and the drag head. When these problems are solved, the drag head will automatically follow the sea bottom, and

dredging pumps and engines of the dredge will be automatically controlled by

microcomputer which processes the dredging conditions continuously. A study

of some of these problems has already been conducted, but more data are

needed.

REFERENCES

1. Hedoro Shunsetsu Shorisen Kaihatsu Chosa Kenkyu Hokokushc.,

March 1977, 2nd District Port Construction Bureau.

2. Hedoro Shunsetsu Shorisen Kyudeikiko no Jikken Hokokusho,

March 1978, 2nd District Port Construction Bureau. 4

376

I.
J. Hedoro Shunsetsu Shorisen Kyudeikiko no Jikken (2nd Report) Hokokusho,

March 1979, 2nd District Port Construction Bureau.

Hedoro Shunsetsu Shorisen Nandei Shunsetsu Jissen Shiken Hokokusho,

March 1980, 2nd District Port Construction Bureau.

Nandei Shunsetsu Jissen Shiken,

November 1980, 2nd District Port Construction Bureau.

Cho Nandei Shunsetsu Gijutsu Kaihatsu Shiken Hokokusho,

March 1982, 5th District Port Construction Bureau.

"Seiryu Maru" no Unko, Seibi, Gijutsu Kaihatsu,

July 1982, Machinery Section, 5th District Port Construction Bureau.

6

-°

377

7•

;F
r-4 -4

0) t4 ..

0 -0 43 

Co3-o

ON c C14 w

Qj~~C WJ 04 4 (

Aj C 0ý C c cn r0 0 w 410 `

0~3

JJ~0 ~JCZ.~ ri 

0.3 0. Cob 4 ~ ~ .1.1 

-'~~0 w3' >1 *.c'- .

Co 0 0 4 -4 7 -4 0 - ca.~ 0 ) ~ - - 4

~~.C (.3 00 00. -4U) = cr c

.1 co Ul 0

00) ca C)' 0 q -4T-4 0 Z

0"0

'n z

$4 ca. ' CD 0.3 1-) C1 W> 2 -3

0.. 3) CJ14' Lr) 9: 0 .0 

'U > 00 h-c' Le) . zV) W0 'UC

4 0-4 0 r-I LNj~ .r m .1- 0 - -. '4 '0 * -=

tA )0. U 03

LrI

N. W ~ M0 'U 0 2 N W A (n u r 0. 0 a U -'-4 co >0 cu-. to4

0 ') U =0 -... w0. 0 4

*-~~ -X0. ~ M0.- &00. '00' 4 .-' m4 1-4 -COX C- -4 ' - 00 -V 00

0 0 3- .33. 0 - cn 0

378
NOTATION

AH Area of the inlet (front) of the drag head (= B-H) km2 )

Ap : Cross-sectional area of the pipe of the drag arm (m )

A q Pressure unit expressed by the height of aqua (water) q

B Breadth of the inlet (front) of the drag head (m)

C Apparent dený.ity a

C True volume density of the bottom sediments

B

C : tverage true volume density 4

CVi: Volume density in the inlet (front) of the drag head

CVm: Volume density in the drag arm

DI Diameter of the mixing blades (m) 4

dH Thickness of dredging (m)

D : Distance from the water surface to ch- dredging pump (m) rp

G : Ouantity of solids dredged per u, time (= C.V-Qm) (m 3/hr)

h Height of the inlet (front) cf the drag head

h: Addedc resistance (m Aq)

hV : Suction pressure (m Aq)

I Plasticity index (%)

M Distance from the water surface to the dredging pump (m)

p

3 0 : Water supplying quantity of th-: dredging pump (m /hr) "0

Quantity of solids forcibly supplied into the drag head

(= Bd 1 -V ) (m 3/hr)

3 Q :Mean ratc of flow (m3/hr)

SDR: Depth of The seabed at the drag head (m)

SDH: Depth of the sole of the drag head (m)

H Velocity of the drag head (m/sec)

V : Velocity of solids in the drag arm ( Qm /Ap) (m.'s)

379
6

V Velocity of water in the drag arm (- Q /Ap) (m/s)

V : Velocity of the dredge (rn/s or knots)

S1

WL : Liquid limit (Z)

W : Natural water content (%) n

W : Plastic limit (Z)

P

W : Water content of pseudo Hedoro (%) " 0

Yb : Specific gravity of bottom materials

Y : Mean specific gravity of slurry m

Ys : Specific gravity of soil particles

Y v : Specific gravity of seawater

T 0 : Shearing strength (kg/cm2 )

T : Dredging parameter (= Q IN/Q .

•oc Dredging parameter at blockage boundary

E Ratio of dredged Hedoro (- (C Qm)/QIN CB)=RR)

40 a : Angle between the drag head and the seabed

0

0

380 ..

S
OVERVIEW OF CORPS RESEARCH PR0OCEA-M ON

DREDGING CONTA.MINATED SEDIMENTS

Dr. R. L. Montgomery

CPT G. L. Raymond

Environmental Laboratory

USAF Waterways Experiment Station

Vicksburg, Mississippi 39180 USA

ABSTRACT

* ~~~The problems of dredging contaminated sediments withextincnvn

*t lonal equipment and techniques are discussed. These problems exist b~cauise

the dredging practices in the United States hlave evolved to achifeve the Igreatest possible economic returns through maximiziniug product ion. As, a re- sult, conventional dredges are not spec if icallv le' i41ned or intende1d for Ilse

in dredging highlv contaminated sediments. However, many feel that dredlges

are thle log!ical, and perhaps only, means of removing, contaminated sed iruents

that have been found in the Nation's harbors and waterwavs. It is als;o felt

that some modifications to eqa.ipment and dredging techniques could resu;klt in

their use in dredging highly contaminated sediments With Minimal adverse im-

* pact on thle environment.

"'his paper outlines active research at thle Waterways Expe~riment stat.iot, on equipment and techn iqties for drL-'Jglng contaminatod sed i'mnts. Tho quiest ion

of dredging in contaminated sedimer ts is being addressed in three wa vs: thle I assembly and evaluation of available domestic and foreign information concernin4 sc imen t rusesion and contaminant release, the developmvint of appro- * priate laboratory tests to pred ict contaminant rel?.ý.se from resuspenided ed imvnts , and *the Ilse of field studies, to monitor pt rformance and comp~ire dredges

ope rat inv unde r var ious cond it ions. P l-ins are dilscus sod for eviltua th, it xist -

in g d rediin4 equ Iipmen t to determine best techn iqu tes for d red giing odiie

that are hi, chlv contaminated with toxic substances-. nit ial field S

hiive a Ire ad v been completed on evalua tin i; sed irmont. resus;pension at thet po in t

of_ dreds ~i u for cut terhead , dustplan, and clamshell dred'dges,. The restiit;ý of

those! proL-iminarv studiles are d iscussed.

I NIROIA'DCTION

tan ~ ~ ~ ~ ~ mliit ~ I/L'ý ~ ,, '41di" totltl5 !Vtois7ttoso r n

t iou ud Nai:t:ceichn jques (10%)TF) Riesearch rr. a

3ei I
I

environmental concerns addressed include resuspension of contaminated sediments and the possibility of contaminant release during the dredging operation.

Although specific dredging operations involving contaminated sediments have

been monitored by various Corps offices and governmental regulatory agencies,

C data are not available on a national basis to allow the prediction of the impact of the operation of a specific dredge in a given situation.

Conventional dredges are not specifically designed or intended for use in

dredging highly contaminated material. However, dredges are the logical, and

o perhaps, only, means of removing contaminated sediments that may be found in

the Nation's waterways. Some modification to equipment and/or dredging techniques could result in their use for that purpose with minimal adverse impact

-: on the environment. In some instances special dredges may be needed for

cleanup activities.

While WES extensively studied the effects of aquatic disposal of dredged

material during the Dredged Material Research Program (DMRP), little research

was done concerning the resuspension of the bottom sediments that occurs due

to the actual dredging operation. The tonr field studies are designed to determine the extent and character of bottom sediment plumes resuspended during

dredging. These studies will provide Information on which to base an assessment of the relative performance of different dredges and dredging techniques

* with regard to their sediment resuspension characteristics.

The introductory work in this area was conducted by Urnard (1978) during

the DMRP. He performed a review of the limited literatur- available on dredgeinduced turbidity. He found that most conventional dredge', create a low con-

.centration plume of silt and clay-sized particles (diameter less than 0.03 mm)

m or Amall flocs (masses of agglomerated particles) that settle independently

through the water column at very slow rates. Although the solids concentrati(ons in the water colhmn in the vicinity of the dredging operation usually do

not exceed several hundred millitrams per liter (mg•/), the particles/flocs

continue to settle until tht solids concentrations near the bortom can exceed

1() vrams per liter (g/,). I'hlis level of concentration (0-10 g/0) of 4uspended

s solids he referred to as turhidity. Concentrations higher than thLs level

take &on wte properties of the naturally ,•currinig "fluid mud" layers which

oftvin form over more dense bottom sediment.

e j-'arct lect ives

libe o, •ect iveq of this research are to develop procedtir,., for pred ict Inv

e, t i ,l r's, IsTtiOT i,)n .rand r lea'. it I :ontaminantq usistnI vatri-U,,s tv,' .s . ,t

,J ,. j.' p, ,,;t ? ' 11n, tvchn i-o s .in i to imprtve and/or developl ni,-w .q |i ;,mv.nt

• mu•d tcinniquve• or ) dt.,-im n'.: !ii.hi%'." contaminated 'dediMcnts1.

c: ,,-,irc::i ..\;'.ro.aclm

.. .. •.'; r',lr'.,.t. iomi ct a.,, ,t.'f .-ith dif tV," l..rerlt- , -

; :• . ,,,: I Ind Lt,c-, i| ;:it.i di.ll I,.- ,ht ,-r-•n ,,d. \v Iil,hl,- .40 ,mv (:,it I ,: thd ,,r,.i,.1•;

at. !'Il It. .t, l'c', . t .1 i ,1 1 i cIltid-, ýi" %-Vt tia t i,,ua l ,1! t Iwo ro-;,, .n 'il-

,, r*Liv t I r ineii pt a ;tatd witb each t" %
* dredge and dredging technique is directly related to the dynamics of the dredg-

* ing operation, an in situ sampling system will be implemented. Sampling will

be performed in the iimmediate vicinity of the dredge, in background waters,

and in ship/barge-generated plumes. Data will be collected at a minimum

around operating cutterheads, dragheads, and clamshells. Any other innovative

* ~systems that max' be available will be evaluated. The operation of each type

of dredge will be varied, to the degree practical, to determine thle relation-

* ship between technique, production, and sediment resuspension. This information will be thle basis for comparing the degree of sediment resuspension

* caused by the dredging equipment and techniques.

The end product of the studies will be a method to predict on a sitespecific basis thle degree and extent of resuspension of sediments and contaminant release fron dredging operations. The predictive methodology will allow

fir sound decisions to be made on selection of the type of equipment required

for drEdging contaminated sediments.

Trhe first phase of the study will be to collect and analyze data available

from various Corps offices and other agencies in order to establish a general

data base onl the performance of conventional dredges. The performance of a

dredge is based on numerous facror,ý and development of a methodology for predictingý, perfor,-mance must consider these factors. Performance data frnm field

* tvsts where parameters are held cons'ant will be us~ed later to develop a pre-

* dictive capability.

* *Data have been collected by several Corps of Engineer-; Districts includinc- the San Francisco, Norfolk, Mobile, New York, and others. This information

will be gathered, analy/ed, and possible comparisons drawn between similar 5dredgLing4 equipment operatingz tinder differing conditions. For each instance,

in! or-.ation concerninmg dredge tvpes, operating characterist ics, sediment types,

hvd -Iraidlt ic nd it ions * meastirement of turbid it\- due to resuspension, ard analv-

, is 01 data coiicvrn in.ý contaminant releas-e Will be coMp iled. Tf possible,

comrpar i.-ons of di ffernt dredge-- and dredging techniques, under similar cond itions will the made. Ile objectivye of comp il1ing t hew; daita is to a id in the

3 i~~!tt rk* dCVe Vtp~Men t of re lait ve rat ing factors for potential resuspens ion of

cortLnitmi itant. f or each o 1 vve'.ral dredging t vpes and d redt' in g cond it ions.

:he D.r~ii4t rict conducted a ma jor field evaluat ion oif two typl.s of

i t"nt :,e isel to d red -e teit Federal channel- in t ho Kep-tne-con tam i mt ed

me i•vt r . hii, orkperit ion p rov.ided an oppor tiintit%\ to compart the perform.,ancý

i0 :on- di t on~il ctitt t.rhvmead rdreL'* aX I Lha 1t Of a dred.ge k t. 'q I Ii I )td V ith . pC

~~cml,! .h- iv mt; t ai Ia p..II parane rlleti tte r w 'tr t cl, l mont 

n :,,' uii d ii tga ti h d.i dt ts p ro vided it -.i vv i n r -

.,I' cOf v ioni anII 1d nonctiC01nvet i onalI equni pmtwnt

i nIsp C Ii Ii. -,td . !redt I't! t" i1;)Tn'!,t wtrev : cd t tct d

* -. "'. *c..i L*t.i. a ncrnw' rtlt.*i.hlldd'

-. * .r it: 1 cd: i nI the %-ict -I !' I i t '.io',al -tt tcr'w.tl

i r ~r ic::' ra-It I, md ! - 4 ' t1,i1.-tr i, i tin I r i~ ind

1,7 SIt , 1 1 i- 1 O l 1 1 1Ct11V !1t 1

r~~ t ~ ~~ ~ ~~~~~ it A t i r , e t

S col 7.1 A1 ~~
q

"A predictive methodology will be developed relying on a factor rating

system for evaluating the performance of specific types of dredging equipment

and corresponding dredging techniques. This factor rating system will be used

to evaluate the potential for resuspension of contamination in the immediate

vicinity of the dredge head. Evaluations of laboratory testing techniques for

predicting contaminant release for specific sediments and evaluation of dispersion using existing models or methods for various hydraulic dispersion conditions will also be completed. All three elements (the factor rating system

"for equipment and dredging techniques, the laboratory test for prediction of

contaminant release, and the evaluation of 'dispersion for various hydraulic

conditions) will be integ-, tted into a matrix approach to evaluate overall

-* potential for contaminant release due to the dredging operation.

The major impetus for these field studies however is not concern with the

*- resuspension of sediment for its own sake, but the fact that the sediments of

many of the Nation's waterways have become, repositories for contaminating

materials. This problem has arisen due to the affinity of these contaminates,

particularly chlorinated hydrocarbon pesticides and PCB's, for the clay-sized

particles and natural organic solids found in most river sediments. When

these sediments are disturbed, such as during dredging operations, contaminants may be transferred back to the water column, either through resuspension

of the sediment solids, dispersal of interstitial water, or desorption from'

* the resuspended solids. Investigation by Fulk, Gruber, and Walischleger (1975)

indicated that for sedirnent-water concentrations of less than 100 g/; the

amount of pesticides and PCB material that dissolved or desorbed into the

water column from the resuspended sediment is neglJgible. They determined

that basically, all pesticide materials were transferred to the water column by

means of resuspension of solids.

LABORATORY INVESTIGATTONS

An evaluation will be made of the applicability of elutriate testing as an indicator of potential contaminant release due to resuspension of sediments

durin4 dredging operations. The existing elutriate test procedures reflect

conditions due to open-water disposal operations. Resuspension during dredgin4 operations involves shorter agitation, times than that resulting from disposal. Modifications to the standard testing procedures will be proposed to

.illow better applicability ot elutriate testing to the case of resuspension at

the point of dredging.

FIELD SiVDY METHO•OLOGY

M,,.t ho•,d ,or .Susrend~ed. S;? irnent- .Measjremen.•t

ýiot-i garnard (1978) ,nd Stern and Stickle (1978) point oiut the problems

n g .i c4aýortonly accepteid method of s•usp.,nded sediment meias.%irement .. ot h

S I tndi" t, t2the ma orit. . of pre. ious ef forts 'were -o.incerned with the me:asurt-ment

rr ,it>. wnici i-i in optica.l propertv ot water. Vurhiditv ma,,suires the

r..,ict iti~ <,W lii ht passalý, through water due to -;uspended particles. I uirh i i iv,

iowev er, *• .nnot ,e c:orr,-J.itted with wei,:ht concentratton of stusiended matter

}- t. O lhet icall' imp,irtant factors of size, shape, ind re•tractive index ot

384
tihe particulate materials bea. little relationship to the concentration and

specific gravity of the suspended matter. This fundamental problem is exacerbated by the fact that there are two ma.or optical means of measuring suspended

sediment level, transmissometery (percent of light passing directly through)

and nephelometery (amount of light scattered). Therefore, results may be

reported in terms of several different types of turbidity units.

Based on these findings, the preferred method of measurement for the IOMT

field studies would be gravimetric rather than optical. This method allows a

more accurate comparison of different dredging operations involving different

sediment types, gives a truer indication of what is actually occurring during

a dredging operation, and permits more precise estimates of the potential

settleable solids. Stern and Stickle (1978) particularly mention the lack of

the latter as a major obstacle in determining the effect of dredging on

aquatic organisms. The gravimetric method used Lhroughout these field studies

is that prescribed by Section 209C of Standard Methods, Fifteenth Edition.

Collect ion Methodology

The decision to use a gravimetric measurement method implied that data

collection would have to be bv discrete point sampling rather than continuous

monitoring. The sampling methodology used was based on a revi=w of similar

WES o-ponsor studies (Nichols, Thompson, and Fass 1978), standard streams suspended sediment load sampling procedures, and experiences of the investigators

durine: preliminary sampling efforts. The methodology was based on vertical

depth profiles taken at increasing distances from the dredge along the direction of current flow.

K rhe actual sampling procedure consisted simply of pumping water from the

selected depth int,) 2f0-ml sample bottles. Current direction and speed were

determined for each sample taken using speed and direction meters attached to

the sample intake. Salinity of each sample was determined in the laboratory

prior to 4ravimetric analysis.

3 FIELD STUDY SITES

St. .;ohns River, 'acksonville

he tirst field study was conducted in .!acksonville, Florida, dirin g

re br.uar v 82 Ficure I). This study directly compared sediment resuspension

o! conventional and waterti-,ht clamshell dredges. Monitorinv and sampling of

5,0t:1 t.it walert ight and open bucket operations were conducted on 9-11 February

19,m2.

h dredý in, w)ork performed during this project was the deepening of the

,r: ,asi:: t, 13 !Uet . Fiz:ure 2 shows the area that had already beel dredced

lrioir t, h taniing. t in, ,• oost of this area had been C'c;ivated to

IS. .t.. t. ,s -an cen, tv0c' time actual samplinv was conducted the

o.runi, n wa.ýs ;ic L-t to the, shore and in shallow water. Indeed, the

:c<n. .k, tile ,,n.r, md the dredte and sckws acted to restrict the flow of

w^atter Iiin the irt-., hetwen the dredgte and the north hbank. The current in

J6
FIIgure 1. e l l n m

11_ý 0 III 1

SNAVA"

A!•q ST~r AT•

• P .- .• " ' or - 6SOZW

Figure 1. General location map for Jacksonville clamshell comparison %

this area was only 0.1 or 0.2 ft/sec. The dredge generally operated for about

10 hr a day (0700 to 1700). This meant a certain amount of flushing could -

occur during "nondredging" hours. During the period of sampling the nondredging hours coincided with the maximum ebb tide. Subsurface data accompanying the bid invitation characterized the bottom as silt (MH) with a specific

gravity of N.4.inety-eight percent of the particles were reported to be

"smaller than 0.002 in. Subsurface investigation revealed the sediment to be

black in color. Inspection of the sediment during sampling confirmed this.

r'lhe waterticht bucket used (see Figure 1) was a modified Yawn-Williams

13-cubic-yard clamshell-type bucket. Mhe modification consisted of the weldin4 of side and top plates onto a standard bucket. The edge of each half was

lined with rubber to ensure a watertioht seal. A rectangular openinV was left

in the top of th' box for the pulley, and to allow air to escape during submmrsion. ihe contractor estimated that the addition of the sides and top

probably increased the bucket's capacity to around 1ý cubic yards. The open

clamshell bucket used on 1(0 February was a standard 12-cubic-yard YawnWilliams bucket.

'386)
RADIAL 3

50

2t40 SCOW 0 ARGE

PIER 139 ~ ST SCOW DR GE

AREA

RADIAL 2

RADIAL 1

Figure 2. Sampling radials, Jacksonville clamshell compacison

Figure 3. Watertight clamshell bucket, Jacksonville clamshell comparison

387
The excavation was accomplished using standard bucket dredging procedures.

Once a:,zhored, the bucket was positioned above the water and lowered open onto

the material to be dredged. The operator found that the watertight bucket had

to be lowered more slowly at the start of the descent to allow the air trapped

in the bucket to escape. Penetration of the sediment was achieved solely by

means of the bucket's weight. Once the jaws were closed, the bucket was

lifted to the height of the scow, swung over to the scow, and the bucket

emptied. The bucket was then swung back to a position one bucket's width over

and again lowered for another grab. Due to the shallow water depth, this

cycle of lowering, digging, raising, swinging, dumping, and return took only

about 45 seconds. The dredge would clear a "cut" about 60 feet wide before

moving forward 4 or 5 feet to the next "cut." The dredge usually wont over a

cut twice to easure proper depth. The average hourly production during the

sampling period was 770 cubic yards per hour.

Barnard (1978) stated that the resuspension of sediments during bucket

dredging was caused primarily by the impact, penetration, and withdrawal of

the bucket from the bottcm sediments. Secondary causes were felt to be 1oss

of material from the bucket as it was pulled through the water, spillage of

turbid water from the top and through the jaws of the bucket as it broke the

surface, and inadvertent spillage while dumping. Barnard also reported that

the Japanese had developed a watertight bucket that caused 30-70 percent less

turbidity in the water column than a similar open bucket. Barnard attributed

this to a 35-percent reduction in loss from the bucket as it was lifted

through the water column and swung over the hopper or scow.

The sampling radials used during data collection are shown in Figure 2.

Data collection was based on the previously described sampling methodology.

Due to the shallow depths, fewer samples were taken than originally planned.

Background samples were taken each day at locations 3500 feet south of the

operation aiong the shoals, and 6500 feet southeast in the main ship channel.

*he background sample locations are shown in Figure 1. All samples taken were

returned to WES for gravimetric analysis.

James River, Vir'inia

WES's second field study was conducted in conjunction with Norfolk District's James River Demonstration Project. The James River, during the period

1967, o 1)75, was polluted with a chlorinated hydrocarbon pesticide known as

Kepone. 1w Kepone becan. adsorbed to the fine-grained, organic-rich sediments

of the river (Hugget, Nichols, and Bender 1980), with the bulk accumulating in

the zone of maximum turbidity in the middle estuary. Within this zone, Kepone

is stored in sites of high deposition, i.e., in dredged ship channels, tribuitary mouths, and reaches of wide cross section where tidal currents are reduced. Because of the Kepone, the Norfolk District, Corps of Engineers, decided to conduct a dredging demonstration project as part of the normal maintenance of the James River Channel. The goals of the demonstration were to

achieve containment of a layer of polluted sediment; minimize resuspension of

sediment at the dredge head; and remove the sediij,:nt at in situ density. In

order to achieve these goals, a dustpan suction head was specially adapted and

388
fitted onl a typical hydraulic pipeline dredge (see Figure 4). The dredge was

operated in the dustpan mode using a dredging method designed to obtain precise

positioning of the suction head within the specified layer of polluted sediment. The dredge was later operated as a conventional cutter suction dredge

under similar conditions for comparison with the dustpan arrangement. The

Norfolk District developed an extensive monitoring program to evaluate the

relative effectiveness of each dredge type and to determine any changes in the

Kepone level, both dissolved and adsorbed. The IOMT field studies were made

in addition to these efforts.

Sampling took place on 27-29 May 1982 for the Dustpan Head Phase and on

9-14 June 1982 for the Cutterhead Phase. The location of both these sampling

efforts is shown in Figure 5. This area is also the "turbidity maximum" of

the James River and was shown to contain the highest level of adsorbed Kepone.

"The channel in this area is 300 feet wide, with a project depth of 25 feet.

In both phases the dredge actually excavated to 28 feet. Subsurface investigation revealed the material to be excavated as underconsolidated silty clay

(CH) with an average moisture content of 144 percent and a wet unit weight of

84 pounds per cubic foot. Liquid limits were greater than 100 with plastic

indices greater than 60.

Figures 6 and 7 show the sampling pattern for each phase. The basic

difference results from the collection constraints imposed by the dredging

methods. During the dustpan phase the dredge moved across the channel, and

was controlled by wires anchored in mid-channel. This limited the collection

area to the edge of the channel for the 100- to 400-foot interval. During the

cutterhead phase, movement around the dredge was less restricted. Additionally, the cutterhead could only dredge half the channel at a Lime, making

estimates of plume location easier.

""The data collected along the radials were supplemented by data collected

in other phases of the overall demonstration project. As part of the evaluation being conducted by Norfolk, a dredgehead collector was attached to the

two different heads. This collector consisted of a line of tubes which

allowed in situ water samples to be pumped to the deck of the dredge. The

samples were pumped into a tank on deck and a transmissometer located within

the tank used to determine the turbidity at the point of dredging. The IOMT

sampling team also used this device to take additional samples for gravimetric

analysis. This device is depicted in Figures 8-10.

PRELIMINARY RESULTS OF DATA ANALYSIS

Jacksonville Clamshell Comparison

The initial analysis of the data from the Jacksonville field study was

accomplished by comparing suspended sediment levels along each of tide three

radials shown in Figure 2. The amount of suspended sediment, by radial, found

at each sample point is ziven in Figures lla, b, and c. These values are

adjusted for the dail; background levels for the appropriate depth. A reading

of zero therefore means the amount of suspended sediment did not exceed the

background for that day and depth.

339
Figura 4. Modif ied dustpan head, James River Demonstrationl Project

./OROAMP r H4ARRISON SAN ( uN~dL or SHOAL 7

DREDGING AREA

A4MfqArrON.

'09

------------------------------
DISTANCE, FT

- - - ~100 200 400 - - -.

FLOW

x

5 0

Figure 6. Sampling pattern, dustpan phase, James River

Demonstration Project

.4

A.°

800

A-,

.I

WFLOW

'8OO

_00

ESSEX o.I100 200 400 8010

S DISTANCE. FT

Figure 7. Sampling pattern, cutterhead phase, James River

Demonstration Project

39

/ DITAN E. . ..
Figure 8. Dredgeheaci collector, dustpan head, .James River

Demonstration Project

Figure 9. Dredgehead collector, cutterhead, James River

Demonstration Project

392
Figuire 10. (01CoItc~IOLI La~nk and t ransmissometer for drudgehead turbidity,

Jaimes Rive~r Demonsitrat~ion Prolect

0

39 3
LE GENO

8 WATERTIGH'IT

200 FT 400 FT mfr

10

Is

20 * * _ _ _ _ _ _

too m0 100 20weus

susmIOto SOIDOS. m4-1

a. Radial I

no0 FT 400 FT OM F

0

100 m0 100 m0 us m~

I ,, I oI I : F

100 F TMI 0OonP

0 t0 t•0 00o zoo too m

SUM) N1O ot ID"

C. Rad ial )

*F igure~I Suspended iolids Itv(-, J ilck-.onfjjo ii amshe11I

ConOr ).tt oi 

)94$
As expected, the results aleng each of the radials were somewhat different. Along radials I and 2 the watertight bucket seemetl to produce reduced

resuspension in the upper water column at distances closer than 400 feet.

Along radial 3 the watertight bucket seems to offer generally reduced resuspension throughout. The 800-foot readings for the watertightýbucket along

radials I and 2 appear to be anomalous, since in addition .o reversing the

trend of lower resuspension for the watertight clamshell tIev also reflect an

increase from the ,tO-toot reading. The reason for this i not as yet apparent; however, it may be due to increased effects of the current at the sample

points farther away from the point of dredging combined wi h a decrease in

!;ample depths from 400 to 800 feet.

Figure 12 shows the average suspended sediment level aken along each

radial. Along both radial 1 and 2 there appears to be a marked increase in

sediment resuspension as we approach the bottom. Table 1 depicts this phenomenon more clearly. ]able I presents the average values of ýsuspended sediments,

by radial, rtr each typ,' clamshell. These readings are adjusted for background.

Ihhe ditfertnces between average values were found to be statistically significant at the 95.' confidei:ce level.

Mhe data In Table I indicate that the watertight clamshell offers a

marked advantage in the upper water colunn over the open clamshell. This

"*I would tend to support Barnard's (1978) contention that the ladvantage of a

watertight clamshell is the reduction in losses as the bucket moves

1 ~LEGIPOD

'. •---,

""WATRTI•"T .AOIAL

44

70

SI1 I I

o so '100 ISO -2W0 2W0

* SuSPfNO4O( SOL 1OS mW1

A r a! F ')A IiAý WaNfO, rl),.

ri ,u r,,I 12. Av,.r, i,+- sii.ýpo,,ndi'd ,edI men.t le've1, bv rad i a 1,

lack- nvills-. Clam-if'll Complir i, on

0

0'r
Table 1. Average Adjusted Suspended Sediment Levels, in mg/l

RADIAL WATERTIG;HT CLAMSHELL OPE.N CLAMSHELL

Upper Water Column

- 1 27 123.25

- 35.6 61.0

80.6 133.3

Near Bottom (Within 5 feet)

1 233 146.6

" 2 300 122.0

- 3 N/A N/A

through the water. Table i also tends to confirm that the major cause of turbidity is the penetration, digging, and withdrawal of the bucket. Figure 13

shows a scale drawing of bucket size to water depth in the channel. As the

bucket is withdrawn, bottom material, particularly in the case of silts, will

slide into the excavated cut. In fact the dredge usually had to make at least

Sone additional pass to remove this material. This leads to an unusually high

level of turbidity in the cut. Since the cut was perpendicular to the current

flow, "flushing" of resuqpended sediment was more difficult.

James River Demonstration Project

3 *The site conditions for the James River Demcistration Project were different from the Jacksonville Clamshell Comparison. All dredging was conducted

in the main channel where the full effect of the tide and current was a factor.

As shown in Figures 6 and 7, the primary collection efforts were taken "downstream" relative to the current. As indicated by Figure 7 only one additional

radial was taken during the cutterhead phase. This was to check dispersion

outside of the main current flow. As seen in Figure 6, due to the unconventional method of dustpan operation and the additional cabling, positioning of

the sample points was more difficult during the dustpan phase. Giver the

general uniformity of sampling and site conditions and the larger number of

data points, average values provided more insight than individual plots.

Two N types of resuspension data are analyzed: that collected by the

dredgehead collector and that collected along the current radials. Both data

iets are considered in comparison and characterization of the two dredging

. methods. Table 2 summarizes the results of the two dredgeheads using only

samples collected by the collector system mr-:tnted on the dredgehead. These

data do indicate a difference in suspended scotment levels at the point of

* dredging. This difference has proven to be statistically significint at the

95;' confidence level. It had been hoped that the dustpan head would reduce

the amount of sediment resuspended at the point of dred!ging. 1i.e data in

Fable 2 appear to indicate otherwise. It is unclear wheth. - this departure

from the expccted was caused by the equipment or by the oprat i': techniques.

The contractor retained by Norfolk District to conduct and evalulta, this

project attributed this departure in his preliminary report, to the better

39f)

4
WATER LINE

Figure 13. Schematic of watertight clamshell bucket operation,

Jacksonville clamshell comparison

Table 2. Summary of Results for the Dredgehead Collector

DUSTPAN cuTTERHEAD

*Average suspended 71.6 40.5

sediment level, adjusted I for background (mg/,.)

*Average current speed (fps) 1.5 0.96

Average salinity (,,.mho) 371.4 199.5

Averag~e wind speed (fps) 14.6 10.7

*hydraulic radius of the cutterhead suction pipe and the difficulties in maintaini:,'; a free flow of material through the dustpan (Mc~anus 1982). Another

factor to be considered was the drodgIALW 'echnique used with the dustpan during

*this study. In this study, the diistioan head was operated perpendicular to the

- current flow.. This method was ust'd to allow more exact positioning of the

* dredceiivad. Byv operating, itn this manner, the dredge was always moving into a

turbidity; cloud. P1h cut terhead was operated generally parallel to the flow,

and, depending4 on its orijentat ion, the current could carry tile plume either

to',,ý;ird or awav from the collect ion tubes. Indeed, preliminary analys is with

rcespect to currkent direct ion s;hows that while the average level of sulspended

seAi~et sdeL!teCted K. the dredvchead collector is haý- ical 11.'lnchanved for tihe

* d'i~'t Pil ead , it iS M,1r'ked I. a ffect el b%- cuirren t for the cut terilead.

*ili re_ I' '0 110W- t h. aive rage %,i liie of Mu 51)Coded solids for all depth11 at

,I 2 1VeIl d i ' [Iace . ho totIii average background leve~l was' ha~is i l lv the sa1me

br Ir ot: usdurrlthe sampling periods. Ilho-; data indicate. that Whilie

,he f,.t2ia%~ c~iu-. mo're upeddsolhis,- near tile point of dredginv, tile

*cut t-erhuid -.'sto c~a'r~ hi hlecr sus.,pended solids level-s at tile g.,reater d i.,-

t'curom' tie poiiut )t Jred ,in,!. ý'igres 15 and 16 are- scilemat ic represent~iL ii L 1:i i%'erag .e vale I, if-tr ea.ch dep;th anld distance sampled. PlieSM va1lues
14-

140

1000 O 0

. s DUSTPAN HEAD

60 BACKGROUND

40 L I I 100 200 400 S

DISTANCE. FT

Figure 14. Depth-averaged suspended sediment levels, James River

Demonstration Project

0 too °0 2 M

.1, 60.0 0 - 0

of *0

-024 %04

2 716 0 * 130 o00i

03 1O! o0?~e .20 e* •eoel

." '47

30 .26

Figure 15. %verage suspended sediment values (rag/;), dustpan phase,

Lames River Demonstration Project

3

" ~398

4
OISTANCE. FT

0 0 50 100 2W) 400 S I I T f"I1

00 011.4 013 021 09.6

II

S10

" 39.5, 011.3 036.8 04&.5 FLOOv 2

•-FL6 

23.4

a 20 %0 2.25 061.75 "50.6 O36.6

. . .o37.5 .55.5 o66.5 037

214

30 -182 ... . 7.131.5 7_ _ _ ,_68

Figure 16. Average suspended sediment values, cutterhead phase, James River

Demonstration Project

are adjusted for the average background value for each depth. Again the cutter.

head resuspension appears to be greater beyond 100 feet than the dustpan.

Also, the dustpan averages (Figure 15) show a uniform distribution of sediment

concentrations, while the cutterhead averages (Figure 16) show no such uniformity, other than a general top to bottom increase. The cutterhead does, however, regain some uniformity beyond 400 feet. Figure 17 is a graph of these

averages superimposed. The different levels of suspended solids with depth

can be more clearly seen in this figure. The dustpan (other than for the

50-foot readings) shows a linear increase in concentrations with depth. The

cutterhead appears to have an exponential increase with depth.

The apparent difference in resuspension characteristics of the two dredges

may be due to several factor.. The most significant may be the basic difference

in the way the dredges e.:cavate the sediment. The dustpan plows through the

sediment, disturbing the particles, and allowing more to escape due to poorer

suction. This resuspended sediment is then carried away by the current and

settles fairly quickly. In contrast, the action of the conventional cutterhead

imparts a greater kinetic energy to the sediment so resuspended particles tend

to travel farther. Additionally, tCe particles may be "flung" upward and then

settle back aýain, giving the nonuniform distributions observed. This idea is

supported by Huston and Huston (1976) research on cutterheads. He concluded

"that by slowing the rotation of the cutter, or even by removing it and using

.ire2ct suction, tLrbiditv could be reduced. Another possibility may be sampling

d di fterences. Vlie data collectod during the cutterhead phase have a high probihiiit%. oi `Oein,, taken from the center of the plume generated by the dredge

IFi c r-r ) . !he restrictions imposed by the dustpan method of operation

ý1-.i:ure ) m:d• center of plume sampling more difficult. The sampling for the

10)0- tO .,-:,-! oO diLInmces Mav hav'e captured only the edge of the plume for

t:1 is ')t tase. her p 1ssibiiites Are differences in environmental factors durinro

":• s.g:p in}: :hoses ,tuchi as current speed.

399

I
J

S

LEGEND

0 DUSTPAN

10 a CUTTER-EAD

50 FT

S100 FT

200 FT

)% '-'-- • 400 FT

020

0 25 so 75 100 125 150 175 200 225 250

SUSPENDED SOLIDS, M919

(ADJUSTED FOR BACKGRMND)

Figure 17. Average suspended sediment levels, by depth and distance,

James River Demonstration Project

400
CONCLUSION

It must be emphasized that this paper has presented an overview of research planned and emerging results based on a preliminary analysis. Much

analysis and interpretation of data remain to be done to resolve some of the

inconsistencies discussed. There is also the investigation and correlation of

production and site factors still to be performed. However, the following

tentative conclusions can be drawn:

a) the watertight clamshell does appear to reduce the amount of resuspended sediment in the upper water column, as compared with a conventional

open clamshell,

b) the dustpan head shows little advantage over conventional cutterhead

suction dredges, and

c) the basic sampling methodology developed is valid and can provide

valuable insights into the sediment resuspension characteristics of dredge

types.

WES will build on the experience and insights gained during these field

studies and conduct further field study during the next two years to obtain

additional data on the operation of existing dredge types and, when possible,

to evaluate new methods or equipment. It is hoped these field studies will

* play a major part in our overall goal of predicting and controlling the resuspensions of contaminated sediments.

REFERENCES

Barnard, W. D. August 1978. "Prediction and Control of Dredged Material

* Dispersion Around Dredging and Open-Water Pipeline Disposal Operations,"

Technical Report DS-78-13, US Army Engineer Waterways Experiment Station,

Vicksburg, MS 39180.

Fulk, R., Gruber, D., and Wallschleger, R. December 1975. "Laboratory Study

of the Release of Pesticide and PCB Materials to the Water Column During

Dredging and Disposal Opexations," Contract Report D-75-6, US Army Engineer Waterways Experiment Station, Vicksburg, MS 39180.

Hugget, R. J., Nichols, M. M., and Bender, M. E. 1980. Chapter 2, "Kepone

Contamination of the James River Estuary," Contaminates and Sediments,

Volume 1, edited by Robert A. Baber, Ann Arbor Science Publishers, Ann

0 Arbor, MI.

Huston, J. W. and Huston, W. C. May 76. "Techniques for Reducing Turbidity

Associated with Present Dredging Procedures and Operations," Contract Report D-76-4, US Army Engineer Waterways Experiment Station, Vicksburg,

MS 39180.

McManus, H. P. 1 July 1982. Preliminary Analysis, James River Demonstration

Project, Contract No. DAWC-65-81-CO013, Amalgamated Dredge Design, Inc.,

Chnerry hiii, New Jersey.

Nichols, M. M., Thompson, G. S., and Fass, R. W. July 1978. "A Field Study of

Fluid Mud Dredged Material: Its Physical Nature and Dispersal," Technical

Report D-78-40, US Army Engineer Waterways Experiment Station, Vicksburg,

MS 39180.

401

p
Stern, E. M. and St ckle, W. B. June 1978. "Effects of Turbidity and Suspended Material in Aq ctic Environments," Technical Report D-78-21, US Army Engineer Waterways Experiment Station, Vicksburg, MS 39180.

40

402
BOTTOM SEDIMENT DREDGE "CLEAN UP"

- PRINCIPLE AND RESULTS -

Eisuke Sato

Japan Dredging and Reclamation

Engineering Association

PROBLEMS OF BOTTOM SEDIMENT DREDGING

Secondary Water Pollution

Most secondary pollution during dredging is caused by suspension of the

bottom sediments. There are two main causes of the scspension. The first is

disturbance caused by movement of the suction equipment. The amount of the

disturbance is determined by the shape and moving velocity of the suction

equipment. The disturbance reaches a large volume when moving velocity is

over a certain value. The second cause for disturbance is water currents during suction. When the pump suction is set in the bottom sediments or sludge,

at first the pump entrains those sediments around the suction mouth and gradually forms many stream-lines around the suction mouth. These stream-lines

disturb the surface of sludge adjacent to them. As the suction mouth moves,

some of the entrained material is lost into the water.

This disturbance is shaped like a bell, with its center located at the

center of the suction equipment. As it is shifted higher, spreading of the

disturbance increases. Therefore, we should change our former thoughts about

suction equipment in order to prevent the occurrence of disturbance and corpuscular suspension.

Complete Removal

Complete removal of bottom sediments containing noxious materials is

desirable but difficult to obtain in actuality.

Bcttom sediments left in suspension after dredging will remain for a long

tire in low density. Elimination of these suspensions is very difficult.

These sediments are left in suspension by two actions. These two actions are

explained below:

a. Before sucking viscous bottom sediments, short-cut flows of low

viscous materials such as water and low density bottom sediments are

caused around the suction mouth, and, as a result, bottom sediments

under the suction mouth remain undredged.

b. Bottom sediments from undredged areas flow into the dredged area during

and/or after dredging. When this stratum of bottom sediments is thick,

the volume of sediments that flow into the dredged area cannot be

ignored.

403

.
The bottom sediment dredging method generally adopted today is the use of

spuds and a ladder. In this case, the ladder will be fixed at a specified

level, creating difficulty in complete removal of . !iments accumulated on the

uneven sea bottom. The generally accepted concept L.. high-density dredging

is the best should be reviewed in order to minimize the residuals of bottom

sediments. It cannot be denied that high density dredging is desirable. However, high-density dredging is only applicable when removal of sediments can

be attained as completely as possible. Therefore, in some instances, careful

dredging work has to be performed that sacrifices high-density dredging.

It is desirable if dredging can be accomplished while minimizing resuspension of sediments and reducing the amount of material left behind, yet

maintaing high-density production. However, we should always be careful that

the environmental effects are not neglected in an attempt to attain highdensity production.

Applications of Conditions and Characteristic Variations of Bottom

Sediments

It is easily understood that the sediments to be dredged are, very unstable

and the dredging efficiency mainly depends on the fluidity of theý bttom

sediments.

Therefore, regardless of the characteristics and conditions of the

accumulated sediments, it is necessary to have 4 redging equipment with adequate adaptability at the suction mouth of the dredging pump. That is to say,

if suction equipment can be developed that can collect a constant quantity of

sediments, regardless of the depth of the accumulated sediments, and average

the mixture of the various characteristics of sediments, we can provide a

constant supply of slurry to the dredging pump in the stable condition by

combining the sensors which can check the conditions of collecting and mixing

of the sediments. In order to realize stable collection and mixture of

sediment, a constant contact betweeen the suction equipment and bottom sediments is needed.

If the suction equipment can maintain these conditions, we can expect

much wider dredging capacity and stable dredging work for all kinds of

sediments.

NEW EQUIPMENT FOR SEDIMENT DREDGING

Function Needed as Dredging Equipment

The final purpose of sediment dredging techniques is to remove these

sediments completely without polluting the surrounding water.

The suction devices generally used for the pump type dredges include a

cutter head or a suction head for cutter suction dredges, and a trailing head

for trailing hopper sucticn dredges.

404

- . . -. - - . .
The main functions of a cutter head are to excavate the sand on the sea

bottom and to assist in suctioning and collecting excavated materials. The

rolling wings of a cutter head uniformly mix excavated materials with water

and guide them into the suction mouth.

A trailing head moves touching slightly on the surface of the seabed.

Water flows through the small opening between the bottom of the head and the

seabed to the center of the head. At the same time sand at the bottom of the

head is sucked into the trailing head.

In order to increase the dredging efficiency, a special type of trailing

head is used. Parts of this head are movable, the opening at the back side of

the head becomes smaller. By decreasing the size of the opening, inflow of

water is minimized. Thus, the dredging efficiency is increased. A study has

already been made on this subject. 1)

Another feature of a trailing head is that it maintains a steady contact

with the seabed.

The development of suction equipment used at present results from long

technical experience. As a whole, they have been so improved that they can

operate with a constant performance as well as function in various dredging

conditions.

Combining these technical lessons with the various problems regarding

sediment dredging, we would like to state hereunder the fundamental conditions

necessary for developing the most desirable suction equipment.

The traditional thought about suction equipment is that materials are

led into the suction mouth by water currents, in which the existe ce of water

currents from outside the suction head is presupposed. At this stage, we

proposea different thought: ve regard suction equipment as "the collecting

equipmtc-IC of sediment." This is based on the concept that it is better to

intercept water currents from outside the equipment, and to wrap these sediments into the equipment in the sediment's original condition. To prevent

water pollution and handle the variety of sediment conditions, the collecting

equipment should possess the movable wings system that can encompass a large

area of sediment. If the collecting equipment has a simple shape such as a

bulldozer's blade, it will be of no use.

The most effective method to completely remove bottom sediments of

different viscosities is to change these sediments into a uniform density and

viscosity. In this manner bottom sediments can be removed completely since

the sediments will then flow regularly. Therefore, it is necessary to equip

the suction equipment with a mixing device. The mixing device should also

enable the smooth movement of water and sediments to the suction mouth. By

fitting the suction equipment with the mixing device, we can expect stable,

operation of the dredging pump and a good dredging result withuut a remaining

undredged portion.

405

i h
The suct'on equipment must maintain a constant contact with the

bottom sediments. One method to make this possible is to control the contact

pressure of all or the suction equipment against the bottom sediments. By

controlling the contact pressure, it is possible to control the submerging

depth of the equipment in the sediments. In addition, it is possible to

dredge the sediments in accordance with the formation of the seabed. The

suction equipment should always be in contact with the bottom at a constant

angle. In order to do this, the suction equipment has to be equipped with a

horizontal controlling device which maintains the angle even if the dredging

depth or other conditions change.

In order for the suction equipment to operate efficiently, it' is

necessary to check the accumulating condition of sediments in front of the

equipment, check the collecting condition, and if possible check the flow:, g

condition. It is also necessary to check the generation of turbidity caused

by dredging. By using sensors to check these dredging conditions, the mosr

efficient operating conditions can be provided by the operator of the dredge.

Dredging Equipment

Based on the functions listed above, we have developed some new dredging

equipment, named CLEAN UP (Figure 1). CLEAN UP is equipped with a movable

. .

111

Figure 1. CLEAN UP equipment

406
* . . -*.V -~

wing in front to overlie the bottom sediments, a movable shutter to intercept

"the inflow of outer water, a mixing device, and sensors to check the dredging

conditions. In addition, the equipment can control the contact pressure

against the seabed, and keep its position horizontal regardless of depth.

Figure 2 shows the structure of the dredging equipment. A photo of Clean

Up is shown in Figure 3.

Dredging Pump

Various types of dredging pumps have already been developed in Japan.

The principal ones are pneumatic, submerged centrifugal, piston, and screw.

For dredging bottom sediments, the pump must possess the following abilities:

a. Stable suction in high density regardless of the water depth.

o. The ability to transfer constant volume regardless of change of

density.

c. Production feasibility of a large capacity.

d. A large passage for rubbish and obstacles.

e. Low equipment and running costs.

Upon examination of these requirements, we chose the submerged centrifugal

pump as the most desirable pump for sediment dredging.

As Figure 4 shows, the submerged centrifugal pump is designed for

dredging bottom sediments, and consists of a submerged hydraulic motor and a

passage large enough for rubbish and obstacles.

This pump (combined with the hydraulic motor) is fixed in front of the

dr.dge's ladder so that the pump is always in the water. The pump is

designed to maintain a constant rate of flow regardless of the change of

drnsity by controlling the hydraulic pump placed in the machinery room. The

rate of flow can be easily changed in accordance with the dredging conditions.

EXCLUSIVE DREDGE

For dredging bottom sediments in Japan, some exclusive dredges have been

constructed. These lr',Les are equipped with suction equipment and dredging

pumps for bottom sediments. The main features of the typical exclusive

dredges are shown in Table 1. Figure 5 shows the general arrangement of CLEAN

UP NO. 3. Figure 6 is the photograph of CLEAN UP NO. 3.

RESULTS

Actual Results of Bottom Sediment Dredging

The number of dredging jobs using CLEAN UP dredging equipment totaled 4

at the end of 1981, and the dredged volume has amounted to about 2,200,000 m

V !407

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Figure 3 o sIv uction equipment CLEAN UP

Ilk

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_ _ _ _ _409
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S....

Fig-are 6. CLEAN UP No. 3

410
L

I

Dredging soils have been mainly soft mud and sand, containing various

noxious materials, for example, mercury, cadmium, PCB, and oily and organic

substances.

Table 2 shows the list of dredging work and removal of bottom sediments.

Relations Among Dredging Conditions, Turbidity Generation, and Dredging

Density

The swing velocity and cutting depth of soil per swing are related to

turbidity generation and dredging density. When using CLEAN UP suction equipment, 3 to 4 m/min of swing velocity is best for minimizing turbidity generation. When the swing velocity is over 3 to 4 m/mmn, turbidity generation

increases.

The adequate cutting depth of soil is 0.4 to 0.5 m. When the cutting

depth exceeds this value, turbidity generation increases and the possibility S.exists of sediments left undredged.

The greater the swing velocity and cutting depth, the greater the

L dredging density will become. Turbidity generation should be within permitted

41 limits by controlling swing velocity and cutting depth. Average density of

dredging using CLEAN UP is 30 to 40%.

-" Turbidity Around the Dredging Equipment

Turbidity around the dredging equipment is always checked through a

submersible TV raiera. Under normal bottom conditions, the actual value of

maximum turbidity is 6 to 8 ppm for sediment dredging. However, the turbidity

value sometimes increases up to 80 - 100 ppm during starting and stopping of

the pump or changing of the swing direction. In these situations, the turbidity will be minimized by our operating techniques..

Results of Investigations about Generation Unit of Turbiditý

Table 3 shows the results of investigations about the generation unit of

turbidity caused by CLEAN UP dredges. A generation unit of turbidity is 3 the'

rtal dry weight of turbidity that occurred d~ring dredging work per I m of

the materials dredged from the seabed (tons/mn).

REFERENCES

1) Wolfram Witt, "Pressure Water Supplied Trailing Suction Heads" 1967,

PROCEEDINGS OF WODCON.

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b . .C . . . . . .
PERFORMANCE TESTS OF PNEUMA DREDGE PUMP

T. W. Richardson

Hydraulics Laboratory

U. S. Army Engineer Waterways Experiment Station

P. 0. Box 631, Vicksburg, MS 39180

ABSTRACT

Results of pumping performance and turbidity generation tests of the air-operated PNEUMA dredge pump,

model 600/100, are summarized. Tests were conducted at

four locations in sand and fine-grained sediments and

in different water depths. The following are described: (a) test locations and characteristics,

(b) data acquisition methods, (c) pumping performance

results, (d) variations in performance with sediment

type and water depth, (e) noteworthy characteristics

of PNEUMA pump operation, and (f) results of turbidity

monitoring. Conclusions are given regarding pumping

capabilities and recommendations made for potential

improvements.

INTRODUCTION

In the period 15 August - 5 October 1978, the U. S. Army Corps of Engineers conducted tests of a compressed-air-powered, solids-handling pump called

the model 600/100 PNEUMA pump. The purpose of these tests was to evaluate:

(a) pumping performance, (b) turbidity generation, and (c) usefulness of the

pump in a number of typical maintenance dredging situations. Items (a) and

(b) were the responsibility of the U. S. Army Engineer Waterways Experiment

Station (WES). Item (c) was analyzed by the U. S. Army Engineer District,

Wilmington (SAW). The purpose of this paper is to present primarily a summary

of items (a) and (b), together with several observations on item (c).

PNEUMA PUMP

"The model 600/100 PNEUMA pump includes several major components. The

pump body (Figure 1) consists of three large cylindrical pressure vessels,

each with a material intake on the bottom and an air port and discharge outLet on top. Check valves limit flow through the intakes and outlets to one

direction only, but air can flow in both directions through the air port.

The three discharge outlets join in a single discharge pipe directly above

the pump body. Attschments may be fitted to the material intakes for

dredging different types of sediments. The model 600/100 pump body is

approximately 4.4 m high by 3.7 m wide and weighs 6700 kg. Each pressure

vessel is 2.0 m high and 1.5 m in diameter and has a usable volume of

approximately 2800 litres.

419
AwJ•

C; IC A

' ou ILE I

Figure 1. PNEUMA pump body

The operating cycle of a single pressure vessel is illustrated in Figure 2. When dredging, the material intake is buried in -he bottom. Venting

the air port to atmospheric pressure causes flcw into the material intake due

to ambient water pressure. This flow continues until the pressure vessel is

nearly full, at which time compressed air is forced into the vessel through

the air port. rhe compressed air forces material out of the pressure vessel

through the discharge outlet. When the vessel is nearly empty, the air port

is vented to atmospheric pressure and the operating cycle begins again. The

pump body consists of three pressure vessels, so their operating cycles are

timed to be out of phase with each other but overlap sufficiently to minimize

discharge surging. An important aspect of the PNEUMA pump's operating principle is that it depends on ambient water pressure as an excavation force.

Therefore, it should excavate more efficiently in deep water than shallow

water.

The timing and speed of the operating cycles are controlled by an

electrically driven, variable speed air distributor (Figure 3), located on

the surface. The air distributor is connected to the model 600/100 pump body

by three 100-mm flexible hoses, each leading to a pressure vessel air port. A

single 250-mm flexible hose carries discharge from the pump body back to the

surface, where it connects to the discharge pipeline. The pump body and hoses

are usually suspended trom a crane or other lifting device for dredging, although other types of support are possible.

420
-1 -o ,AA . t 'tM. eAr -.

it VV- .".41 ~

Figure 2. PNELMIA pressure vessel operating cycle

NF r0 PRE SSuRF

VE SSFL

kLEVATION

11~~AI f1 -C~

Pý.AN VICW

IFi~jt 3. INh IAt air d is t r buitor

421
TEST PROGRAM

The model 600/100 was tested at four locations: a river channel, a lock

approach, a tidal inlet, and a dock area in an estuary. The characteristics

of each location are sui-rized in Table I and Figures 4-7. The test configuration ot the I'NELMA pump and supporting equipmfent Is shoan in Figure 8. At

the river chainnel test site, only water was pumped. Therefore, the discharge

was placed directly back into the river. At the lock approach and dock sites,

th'o di'scharge was pumped into a hopper barge for disposal at other locations.

At the tidal inlet, material was pumped through a 2 50-m-diLame ter steel pipel ine of varying length.

TABLE 1. PNELMA PWMP rEST S11E CHARACTERISTCS

S~-.-.-. -- ------- .-.- .. . . ..---.-.-

Water Sediment Sedimn S ucini Test

r'est Site Dv 1)thI Sediment d 5 0 specific Distance Period

o c at i on ~ Vm e() Ga~~m ~ as

River Channel 3.0-9.1 Water - 35 10

Lock Approach 1 .8-3.4 Sand 0.6 2.11 35 8

lidal !nlet 3.0-4.h Sand 0.4 2.01 128-6i0* 11

Dtk3.7-10.7 S II t/C I ay 01.008 1.O9** 35 16

1.51

* P1plt~i itt length was ch~ange~d several timesi during tes4ting.

**Varied with locvition anid depth In s-tdinfent.

SCALE

100 0J 100 2M0 300 M

PUMPINGNN C

'422
LOE fA

ILILI .41 ELEEL V, 'I

(:pum4f

k~/J AREAS

4 2 3

,gn• 1

SF~Iigure 5. [,wtk apprt~ach test site

* ' . ' Ift 

" lin:,r, l .~1 in e •• .• t

•i- lzi23

O

*1

* A considerable amount of support equipment was needed to conduct tests of

*- the PNEUMA pump. A 32-m-long vessel was used to carry the pump body, air

*. distributor, hoses, accessories, instruments, and air compressors. An 18-ton

hydraulic crane on the vessel lowered the pump body to the bottom and raised

it back to the vessel's deck. A 4 4-m-long self-propelled hopper barge with a hopper capacity of 241 cu m was needed at two sites to receive pump discharge.

Air to power the PNEUMA pump was provided by two compressors, each capable of

supplying 29.7 standard cubic meters per minute of air at 6.89 bars pressure. Part of the compressors' output was vented to the atmosphere through a bypass valve prior to reaching the air distributor. The PNEUMA pump operator varied

the bypass valve opening as a crude method of regulating airflow into the air

distributor.

As shown in Figure 8, several instruments were used to measure and record

'parameters describing pump performance. Air flow velocity, temperature, and

pressure were measured by an instrument which converted these values to a standard volumetric flow rate. The PINEUMA pump discharge pressure was mea- sured by a transducer located just above the pump body where the discharge outlets join. Discharge velocity was measured by an ultrasonic doppler velocity meter, and discharge specific gravity was monitored by a nuclear density

meter. Values of airflow rate, air pressure, pump discharge pressure, discharge velocity, and discharge specific gravity were recorded at 10-second

intervals on a multi-channel strip chart recorder. Continuous recordings were also made of two of the measured parameters, usually discharge specific

gravity and either pump discharge pressure or discharge velocity.

TEST RESULTS

More than 51 hours of pumping data and 4 hours of turbidity measurements were collected during the PNEUMA tests. The pumping tests were conducted in

a series of 61 test runs, each run lasting from 20 to 70 minutes, with a typical run averaging 45 to 50 minutes. Data from the runs were compiled in three .. ways: (a) plots of airflow rate, discharge velocity, and discharge specific

gravity tor each run; (b) histograms of discharge percent solids and in situ Sex:cavation rate for selected portions of certain runs when the pump was performing well; and (c) tables of interpolated synoptic data on airflow rate, air pressure, discharge velocity, discharge flow rate, discharge specific

r-arity, discharge percent solids, in situ excavation rate, discharge pressure, total di ,barge head, puTp input power, pump output power, and pump efficiency. ocr discus.ion purposes, pump performance data are grouped according to whether

the px'ip was discharging water, sand, or fine-grained sediment (silt/clay).

T he results of turbidity measurements are treated separately.

Water Tests

r Three test runs were made in a river channel with the PNEUMA pump dis- * charging clear water. During each -un, a valve on the discharge pipeline was (2closed in a series of steps to produce increased discharge resistance. Water " depth over the pump was also varied from 3.0 to 9.1 m. Figure 9 shows the

airtlow rate and discharge velocity for one test run made at a constant water

depth of 6.0 m. T'he effects on discharge veloc:ity of closing, the discharge pipeline valve are seen in the period from 15 to 30 minutes. With the valve

0 fully open, discharge velocities were approximately 4.2 m/s. Closing the valve

in steps to approximately three-fourths "closed caused velocities to drop to

425
LJ

L. 60

.CC G tICJtIN~t YARV 8 -,1 78

RUN= SEC. 50

440 2-

20

CrO 8CC !16 -120

-c.O 5.0. :0.0 15.0 20.0 25.0 30.0 35-C 40.0 45.0 50.0 55.0 60.!

TIME.. Miti.

L& 2C C r--NE YAR 18 7q 6

' C, ~RLN: E: 1 

• _ ',. 6. C0 >-5

- 3 >

~8 C UmA 'r r, 4 

aC 6. 0.0 C 5.0 20.C 25.0 30.0 35.0 40.0 45.0 5G.0 55.0 6G.C

T I ME, M! .N

Figure 9. Example airflow rate and discharge veloc.ity,

water tests

"approximately 2.1 m/s. During the entire run, the airflow rate remained

- roughly constant at 21 to 22 standard cubic metres per minute. Efficiency of

* the PNEUMA pump during the water tests, expressed as the ratio of pump output

power to pump input power, was usually in the range of 8 to 12 percent.

. Data taken during the water tests indicated that the airflow rate required

by the PNEUMA pump for a given discharge varied directly with the depth of

Swater over the pump. This should be expected, since the PNEUMA pump operates

• on the positive-displacement principle using a compressible "piston" (air).

Since airflow rate is roughly equivalent to power, this means that power

required by the PNEUMA pump varies directly with depth for a given pump output.

For a centrifugal or conventional piston pump, depth variations have only

secondary effects on power consumption.

"426
Sand Tests

Sand wns pumped at two test sites - the lock approach and the tidal inlet.

The lock approach sand was coarser and water depths were less, but the pumping K distance there was several times shorter (see Table 1). Because of the shallow water depths at the lock approach, the PNELTMA pump experienced some difficulty in excavating sand there. This also limited the airflow rate which

could be supplied to the pump and, consequently, discharge velocities at the

lock approach were relatively low. However, most phenomena related to operation of the pump were similar at both sites and can be discussed together. A

I summary of the more important phenomena noted during the sand tests is as

follows:

a. The pump discharge specific gravity was usually considerably less

than the in situ sediment specific gravity. Figure 10 shows a composite histogram of pimp discharge percent solids and corresponding values of specific

gravity which represent the periods of best performance in sand. The predominant range of discharge percent solids by volume is 10 to 25 percent, corresponding to specific gravities of 1.17 to 1.41.

b. The, pump discharge showed significant, systematic variations in specific gravity and velocity which can be related to the way in which a PNEUMA

*g pump operates. Figure 11 shows part of a continuous record of discharge specific gravity made during a test run at the tidal iilet. A repeating variation with a period of 33.5 seconds is evident, corresponding to the time re- quired for the air distributor to make one cycle through all three pressure

vessels. Within a single cycle, three distinct peaks appear, each representing the discharge of a single pressure vessel. At the same time, discharge A velocity usually varied in a similar manner. Figure 12 shows a continuous

record of discharge velocity taken when the air distributor was run at a slower speed with a cycle time of 45.5 seconds. Again, the variations due

. to each pressure vessel are evident.

c. Pump discharge velocity was observed to vary inversely with discharge

specific gravity, especially at lower airflow rates. Figure 13 shows this

relationship, and also shows that the velocity dropped' to near zero when discharge specific gravity approached an in situ sediment value at 13.0 minutes.

The velocity/specific gravity relationship was also observed at higher airflow rates, although the variations were less pronounced.

* Fine-Grained Sediment Tests

Tests pumping fine-grained sediment were conducted at one location, a

dock area, in water depths deeper than for the sand tests. The sediment

pumped was relatively unconsolidated and easy to excavate. However, unlike

sand it would not flow to the pump by gravity when an excavation was begun. • Therefore, the pump had to be moved continuously by the boat while pumping

to obtain a constant source of sediment. Results of the fine-grained sedimont tests are summarized as follows:

4

427

S
1.0 1.1 1.2 1.3 1.4DISCHARGE SPCIFIC GRAVITY1. 20 2. 22

1.0 12 .1 1. IA .S 1.0 1.7 tIi 9 . 2 .

'0

0

0

*0 5 0 '5 20 25 .10 40 45 50 55 60 .'5 70

DISCHARGE PERCENT SOLIDS

Figure 10. Composite histog'ram, discharge perctnt

solids and specific gravity, sand tests

4-- J 4.

4-4

t + tmtiF

-i r

42

7 4
>- ..... , ,. .. .. .

.. .. .. .. . .;.. i • ] i " ] ' i .... ] i i ' .... i ] i .... ] • '; i, • t; • ; ,•i; ;

32.0 T2ý,min 24.0

Figure 12. Example discharge velocity, sand tests

a. Pump discharge specific gravity was usually within the range of measured in situ sediment values when the pump was operating well. Figure 14 is

a composite histogram representing periods of good pump performance.

ib. Most phenomena related to pump operation were similar in nature but

of less amplitude than in the sand tests. Discharge specific gravity variations appeared to be connected more to problems in obtaining a constant sediment supl-ly for the pump than to. the way in which the pump operates. When

pumping well, the discharge specific gravity at times was almost constant

(Figure 15).

c. T'he PNEUMA pump was able to produce a more constant discharge specific

""ravity in fine-grained sediment than in sand. However, the method used for

deploying the pump in fine-grained sediment made it difficult to continue

pumping sediment for periods longer than 10 or 11 minutes. In pulling the

pump along the bottom, the material intakes thay have changed position often

and the pump may have moved in and out of sediment layers.

Turbidity Generation Tests

Water samples were collected at 10-minute intervals and four water depths

during three PNEUMA pump test runs in fine-grained sediment. Samples were

taken adjacent to the pump and downstream at various distances to measure both

turbidity generated at the pump and the extent of any turbidity plume. Before

each run; samples were taken to determine the levels of naturally occurring

turbidity. Each sample was analyzed for suspended solids in milligrams per

litre and for turbidity in Nephelometric Turbidity Units.

Results of the turbidity generation tests were somewhat inconclusive.

.here was evidence ot some turbidity generation by the pump, especially in the

lower water column, but the turbidity was generally short lived. Figure 16

shows the time history k : suspended sediment values for one run for samples

tiken db-wstream of Lh'. -ump. During this run, the PNEUMA pump discharged

an in situ density slurry for four time intervals totaling approximately

• 12 minutes. This discharge correlated roughly with the increases in suspended

sediment seen in the latter part of the test run in Figure 16. Other test

runs produced similar results; however, in all cases the periods of high density discharge were too short to determine what the fully developed turbidity

'" levels might be after sostained pumping. The levels measured did not repre-

"sent excessive increases over naturally occurring values.

429

S
. C •r • : Oc SEC ! 8 '

-50

1 ~.6CC' Q ~-40• Z

30~

CD 0

-4 114RIMC-

'r 4,S6h

-10

.C 5.C C.0 :5.C 2C.C 25-C 30.0 35.0 40.0 45.0 50.0 55.0 60.0 I ~TIM1E, • IN.l

-'-8'.CF L-Cr I ." , 8 Z3 7, 6

C,.RUN: ;"O Si',-.

40

- 4 .3w•

*0- - 10F

'2'.C "0.0 5. ;5. 20.0 . .. 30.25Th.O 40.0 .. 4 5.05 .0 55.0 60.0

"•- r L7C s'P , :- 78 -

C'-.

6C-2

(.,Cr~

.0 .,6c

-0S :. 0 -0. 15.0 0. 25.0 30.0 35.C 40.0 45.0 50.0 55.0 60.0

T IW' .4 ) N

Figure 13. Example airflow rate, discharge velocity, and

discharge specific gravity, sand tests

P •N .0 .;C I o . . o . . o . - • . . .
DISCH4ARGE SPECIFIC GRAVITY

1.0 1.1 1.2 1.3 1.4 1.8 1.6 1.7 1.8 1.9 2.0 2.1 2.2

70

~6U

2'

so RANGE OF IN SITU

SEDIMENT DENSITY 1

30

2.0

10,

50 5 to 15 20 25 30 35 40 45 so 55 .60 65 70

OISCHAPGE PERCENT SOLIDS

Figure 14. Composite histogram, discharge percent 3 solids and specific gravity, fine-grained sediment tests

1 2. I4t 1

4 tlt tý

ik 111i* II Il III 5 i11 - ýj ;j3 4 t ! , 1

... .. .4:................... .. 

16.0 ~Time, mi8.

Figure 15. Example discharge specific gravity,

* fine-grained sediment tests

431

A I
50 - 6 METRES DOWNSTREAM 30.5 METRES DOWNSTREAM OF PUMP

U OF PUMP

S40 - S4 SAMPLE DEPTH,

0. METRES

---- 0 1 <I

r _ _---- 1.5

9 30 3.0

z

z20

w

U,

z 10

.

o, .. .. ,. .. . . , _ _ ,. .i

01

0 10 20 30 40 50 60 70 80 90

TIME, MINUTES

Figure 16. Example suspenced sediment values downstream

of PNEUMA pump

CONCLUSIONS AND RECOMMENDATIONS

The following general conclusions were drawn from tests described in

this paper:

a. The PNEUMA pump could remove fine-grained sediment from the bottom at

an in situ density but could not achieve the same results in sand.

Sb. High density discharge could be sustained only for short periods,

usually 15 minutes or less. This was caused in part by difficulty in deploying

*the pump properly and in part by shallow water depths and compacted sand

making excavation difficult. It was observed that the pump could excavate sand

only in water depths greater than 2.5 m.

c.. The PNEUNA pump has a low power efficiency compared with a centrifugal

dredge pump. Calculated efficiencies pumping water, sand, or fine-grained

sediment were always less than 20 percent and often less than 10 percent.

432

'Il
d. The PNEUMA pump appeared to generate some turbidity when dredging

fine-grained sediment, but the relative increases measured were not excessive

and could only be loosely correlated to pump ý,,eration. It is possible that a

better method of deploying the pump than that used in these tests would lower

turbidity levels even further.

Some areas for potential improvement of the PNFUMA pump are suggested as

a result of these tests:

a. Reduce pump size and weight to make handling easier.

b. Replace mechanical air distributor with valve system on pump body.

This would eliminate two air hoses and possibly reduce air energy loss•.

C. Add vacuum system to pressure vessels to improve shallow water

performance.

d. Improve pump efficiency by reducing energy losses within each pressure vessel. One way cf doing this would be to improve the system of check

valves and pipe inlets which handle flow within each vessel.'

e. Develop better methods for deploying the PNEUMA pump, using more

rigid, controllable support systems built specifically for the pump.

ACKNOWLEDGEMENTS

The investigations described were accomplished using funds provided by

the Office, Chief of Engineers, U. S. Army. Permission was granted by the

Chief of Engineers to publish this information. The author wishes' to acknowledge the contributions of the following persons in collecting and analyzing

the test data: Mr. J. E. Hice, Jr., Mr. R. A. Shafer, Mr. J. D. Ethridge, Jr.,

Mr. J. D. Tarver, Mr. E. W. Flowers, Mr. S. E. Varnell, and Mr. W. C.

Strahan, Jr. The author also thanks Mr. W. H. Sanderson, Mr. D. M. Howard,

and other personnel of the Wilmington District for their support during the

test program.

433

! "'
SEDIMENT RESUSPENSION IN THE VICINITY

OF THE CUTTER HEAD

Hiromi Koha

Toyoaki Shiba

INTRODUCTION

Dredging work in Japan has been conducted, in most cases, by cutter suction dredges. This method has a greater dredging efficiency as well as a

wider range of application to cope with the conditions of exe'ution relating

to soil, water depth, discharging distance, etc. At the same time, it is

known that when the bottom material is dredged by a cutter, the fine-grained

dredged material is suspended, thus causing sediment resuspension in the vicinity of the cutter head during the dredging operation.

In Japan, many marine products have been used for food since ancient

times. In recent years, culture fishermen of sea breams, young yellowtails,

oysters, lavers, etc., have become quite active in the sea off the coast,

thanks to the progress in culture technology.

It is feared that resuspension from dredging work conducted i.n the sea

adjacent to culture farms will adversely affect fish and larva. Hence, the

period of dredging work is often restricted and other dredging methods causing

less sediment resuspension are often adopted instead.

In order to continue using the efficient cutter suction dredge while coping with the resuspension situation, it is first necessary to understand

sediment resuspension in the vicinity of a cutter head. We decided to study

sediment resuspension and work out measures to prevent it by conducting an

indoor modeling test of the cutter.

DREDGING OPERATION

The usual method of a cutter suction operation is to fix its stern by a

spud and let the end of a dredge ladder extend from its bow into the seabed.

The bottom material is then dredged by revolving the cutter attached to the

end and pumping the material up with the water.

Various shapes of cutters are used according to the nature of the soil.

The standard cutter (Figure 1) has blades virtually parallel with a cutter

shaft and a suction mouth installed behind the blades.

434

S... .

,I
seabed

.*edgtng soil th ickness 0 r de-m t r a

Figure 1. Cutt'ý.g operation (side view)

The bottom material scariri~d by cutter blades moves toward Lhe suction

* mouth with the water entrained pulled in by the dredging pump and the screw

operation of the blades themselves. Some material is left in thle dredging

track behind the cutter. The? direction of the cutter revolution is fixed

clockwise regardless of its ',wing, direction. The cutting operation of the

bottom material vari2s according to the direction of swing as shown by

Figure 2.

* Left swing

seat~ ~ ~ ~ trane watergl ~ ~ rdgn

0 Figure 2. ~~Cuttier obrlioafrntdew

Seabe dreded ma435 a

reann
Figure 2 shows the condition of the cutter seen from the side of a dredge.

* In the left swing direction, cutter blades cut up the bottom material from

beneath; this is called "under cutting." In the right swing direction it is

called "over cutting." As is clear from Figure 2, dredged material is easily

supplied to the suction mouth in the under cutting since the blades scoop up

the dredged material from below. In the over cutting, however, the blades cut

the bottom material from above and splash the dredged material under the

cutter and opposite the swing direction, thus making it difficult to deliver

the dredged material to the suction mouth. Therefore, under cutting has a

higher concentration of dredged material than over cutting and the axmount of

material left behind is smaller. Concentration in this case means the per-

,centage the bottom matcrial dredged from the seabed occupies in the mixture

"sucked by a dredging pump. rhis concentration is also used as an indicator of

dredging efficiency.

When an operator engaged in the dredging work wants to increase the

dredging efficiency, he generally matuipulates levers to increase the amount of

dredged material by increasing the swing, speed and the dredging soil thickness.

The cutting ope'rat ion, as mentioned above, varies considerably according to

the swing direction. Hence, a studv was conducted on the effct of swing

direction on sudiment, resus.pension during dredging.

SJudiing from Figures I and 2, sedimetint resuspensfon res'ýtts in the vicinity of the cutter head as fine particles of the dredged mi.n:-rIaL are left

behiod floating and suspended. It is bl.lieved that incrt-as. i dredging soil

thickness and -wini, speed .is well .as use ot t he right suwing .jireeL i.tin catise

st•.idmnt restispens Ion. I f the cuttetr revolition i's incrvasiii, the- centrifugal

force on drdi-,ed materi.al and wiater flow in the vicinity beccon.s greater, thus

prvsimnabliv in crto.•sing the anitint of the sediment resuspenston. i'hi,. viewkd,

the opteraition desiined to incrvase the drv dginsn efficiency generally increases

t:at, sudimitot risuspension In the vicinity of thet cutter head.

-EXIRIH'WNI 10 KI)CRFL\SE S.DI*MNT R.SUSPENSION

F.Ictors cais inug -ivdimnent rv-o ispension by a cutter stiction dredge include

natural cndtition, rl.iting to thi, -o i l and tid"S as Well .'1s tilth optotat in

conldIt ition, l.it, ng to' tiht' spet-d of cutt ttr rtv, v lutiton, %wing sipot,.di, and Ohape

o1 ,. Cut t *tr t iC. iOf thiisi* factors,, *,e•a,•ures most likely to decrt-.asoe stdirenttt

n-'s',i',iw I', n irv t hose concerned with theie op,-r.atlnu condItiorn.. Rv oxp,,ri,,nc(,

v it . thu:,'t thit the following" ste.ps sho ld ht, taken to decrease restuspension:

.1. Slow d. 'wi cutitter revo lut i oil.

,). Slow down swiniv 41ped.

C. .t Iut irvtdi t fro-' the' -romid -4irf.ict mim decre,.se thet-

• oil thic .kne-• to :! drvdevd Y. ., citt,.r at 4 t i:','.

.r,'.is thw imotint ot wt,-r to h p, :' d.

tit, o ,r-t i . it'lint iu l ,thovey irit,e ! c,'Ct lv', in decreasig .. d ir!rtnt

r,.,¢ p-¢p, ion, hut t u!i c lso te(.!d t. ,I cr. t tht dr.d ing e ic,.C" .f

• ,,rdr to r"jni:'j i, L t-' i. di 'iint ro, ,. ' i- ,, .itliuu t .reatlv. lo iw, ., t:i,

0"

I-
dredging efficiency, it is necessary to prevent the sediment resuspension

without greatly changing the existing dredging mechanism. There are many

* factors causing the sediment resuspension in t'he vicinity of the cutter head,

but the biggest factor is believed to be the scattering of the dredged material

by the centrifugal force of the cutter. Therefore, it was thought that a

cover around the cutter may help decrease the sediment resuspension in the

vicinity of the cutter head. A modeling test was conducted to ascertain the

effect of the cover. The basic design of the cover was such as to enclose the

cutter. However, a study was also made of a side cover in the swing direction

which could De closed and opened. A front cover that may obstruct the flow of

the dredged material was designed to be removable.

W)DEL TEST

Basic Policy of Experiment

The experiment of a model, unlike that of a prototype, is subject to

various restrictions. In this regard, a basic policy was adopted to conduct a

study on the following three points:

a. The mechanism causing the sediment resuspension in the vicinity

of the cutter head.

b. 1he effect of preventing the sediment resuspension by the cutter

cover.

c. ['he effect of a cutter cover on the dredging efficiency.

1.kst Methods

In the experiment a 4,000-p.s. pump dredge was used as a prototype and

tihe Froude model rule was applied at a scale of 1 to 25. The operation condit ions of the prototype and the model are shown in Table 1.

Fable I. 0perati~nr Conditions of Prototype and Model

------------------.. rotot;R.. Model

PI~mpiog 5000 m 3/hr 27 ;/min

* wiS'ý: Spee.d 10 M/rMin 6i0-20)0 cm/min

Cu tt-.r 20 rpm 100 rpm

rovo/I i i t i o n

drtd.:in• 1-3 m h cm.

soil tilickness

0 ~------------------ -- - -

,;!t,-, iM ,.•t '! ,r . conducted 'w i ti / iotus •perat ing co td it ions

i:..d ,..ct or 5'.': . he ex ts. ;ri'e ,rL' ilso carried out on

t r,'i rertint kidts ,:-, ls: a starndard t%'pe cutter model, a model

437
equipped with a cover as shown by Figure 3, and a model whose front cover was * removed.

main cover mi oe

ladderfrncoe

cutter shaft

side~~~~-sd Cut oeverOlgft~dJ 

4 Figure 3. Cutter cover model

Vest Results

Hiei tes~t resifits are shown in Figure 4 for sediment resuspension and in

Fig~ure 5 for dredging efficiency.

150 _ _

Over cutting

*9

15 Under cut t

Under cutting

with cover

0 50 10 ;50 20 250 * Swing soeed (Cm/mini

Figure 4. Sediment resuspension

438
15

\ Under cutting

\with cover

Under cutting

-10

C

SOver cutting with

C, cover

"Over cutting

I

0 5•0 IC0 150 200 250

Swing speed (cm/min)

Figure 5. Dredging efficiency

It may be problematical to draw a quantitative_ conclusion on the basis of

the test conducted alone; however, we believe a considerable trend concerning

sediment resuspension and dredging efficiency could be detected. The following are some of the salient points of the result of the modeling test:

a. Sediment resuspension in the vicinity of the cutter head is

caused by floating and suspension of the dredged material

scattered radially around the cutter mainly due to the

cutter's centrifugal force and the dredged material remaining

0 on the track behind the cutter.

b. When there is no cover, the effect of the water flew caused

by the revolution of the cutter is great in the area where the

swing speed is low and the sediment resuspension increases.

This sediment resuspension t.•,idly decreases in the under cutting

mode at a swing speed of 100 cm/m~ii (prototype: 5 m/rin); in

the over cutting mode it slowly decreases up to a swing speed

of 220 cm/min (prototype 11 m/nin).

439

0.
c. When a cover is installed, the sediment resuspension occurring

at a swing speed of 180 cm/min (prototype: 9 m/min) is very

small.

d. With or without a cover, the sediment resuspension increases

when the swing speed is over 180 cm/min (prototype: 9 m/min).

"This is largely due to the dredged material remaining in the

track behind the cutter.

e. When the front cover is removed, the sediment resuspension

increases greater than when it is equipped with a front cover

when the swing speed is over 180 cm/min (prototype: 9 m/min),

. .but it is still good enough to prevent the sediment resuspension.

f. Dredging efficiency is shown by concentration. In this

experiment, the over cutting concentration is about one half

that of the under cutting.

&. When the cover is installed, the concentration increases. In over cutting, the concentration becomes twice as much as when

there is no cover.

h. When the front cover is removed, the dredging efficiency value

stands halfway between the value when there is no cover and when

a cover is installed.

As a result of the model testing, it was confirmed that the cutter cover

is effective in preventing the sediment resuspension in the vizinity of the

cutter head and increasing the dredging efficiency. It was particularly

effective when over cutting. It was also confirmed that, even if a front

cover is removed, the effect of preventing the sediment resuspension is not

much different when there is a cover and the swing speed is below 180 cm/min'

(prototype: 9 m/min).

CONCLUSIONS

The modeling test was successful in finding out the mechanism causing the

"* -sediment resuspension in the vicinity of the cutter head and confirming the

effect of preventing the sediment resuspension by a cutter cover.

However, many problems still exist that have to be solved before the

"cutter cover can be used practically. Further studies are needed on the

structure of the cutter cover, operation of dredge, etc., from various angles

so that a test can be conducted on an actual dredge in the future.

BIBLIOGRAPHY

Shosei Iwata. 1960 (Mar). "On Cutter of Pump Dredge." Work Vessel.

Teishitsu Joka Kyokai, Inc. 1975 (Mar). "Study on 3ediment Resuspension by

Model Testing (Part 1). A research report on the disposal methods, etc.,

of sludge in river and sea."

440
Tokuji Yagi. 1975 (Nov). "Research on Sediment Resuspension by Pump Dredge."

Work Vessel.

Leon W. F. Joanknecht. 1976 (Jul). "A Preview of Dredge Cutter Head Modeling

and Performance," Wodcon 7.

I

0

441

S.
THE LONG-TERM EFFECTS OF DREDGING OPERATIONS PROGRAM

T. R. Patin, T. L. Hart, C. C. Calhoun

Environmental Labora tory

U. S. Army Engineer Waterways Experiment Station

P. 0. Box 631, Vicksburg, MS 39180

ABSTRACT

In October 1982 the Long-Term Effects of Dredging Operations (LEDO) Program was authorized, funded, and initiated under

the sponsorship of the Office, Chief of Engineers (OCE). The

stated objectives of LEDO are to provide new or improved state-o

the-art technology for predicting long-term environmental impact

of dredging operations and to improve or develop methods for min

mizin& any adverse impacts associated with dredged material disposal. The program presently consists of five separate but high .y

integratedwork units in two general work areas: effects of

aquatic disposal and effects of upland disposal. LEDO is planned

as a continuing program since applied environmental research mus'

address current problems and research priorities are subject to

change. The program is managed under the Dredging Operations I

Technical Support (DOTS) Program at the t.kterways Experiment Stat

tion (WES). This paper presents the status of the program in its

present form and its aims in the near future.

INTRODUCTION

Bac kg round

By the early 1970's, concerns over the environmental effects of dredging

operations reached the stage where Federal legislation mandated the Corps of

Engineers (CE) to undertake a major study to determine the environmental

effects of dredged material disposal and to develop procedures for minimizing

any adverse effects. To this end, the Dredged Material Research Program (DMRP)

"was initiated in 1973 and successfully completed in 1978 at a cost of approxi-

* mately $33 M. The DMRP provided the first definitive information on impacts

"of dredged material disposal and dispelled many fears expressed at the time.

Due to the relatively short time frame of the DMRP (5 years) , all questions

related to long-term effects of dredged material disposal could not be!

addressed.' Through the Dredging Operation Technical Support (DOTS) Program,

estabiished at the completion of tha DMRP, low-level monitoring efforts at

* selected DMRP field sites were undertaken and limited studies have been under

way to develop first-generation procedures to evaluate long-term effec s.

4

442
These efforts have allowed the CE to continue to significantly influence the

direction of criteria and guideline development on . national and international level as well as resolve on an interim basis interpretation conflicts

with other regulatory agencies. These conflicts, however, have resulted in

costly delays on major Federal as well as non-Federal projects.

In early 1980, the CE realiAed there ws a critical need for research on

the long-term effects of dredging operations. The Long-Term Effects of Dredging Operations (LEDO) Program is designed to address these critical needs on

r a continuing basis. The specific work units were Jdentified and developed

based on hig;h priority needs subomitted by the field (Table 1), close coordination with the field through the DOTS Program, and consultation with EPA and

other regulatory agencies. The integrated work units allow specific problems

of nlational concern to be addressed while maintaining the flexibility to

address future needs resulting from changing environmental legislation and

interpretation of regulations. The work units are grouped into two general

work areas:

a. Effects of aquatic disposal.

b. Effects of upland disposal.

0 The present research program (FY 82) consists of five separate but highly,

integrated work units in the two general work areas. The work units are

planned on a five-year basis; however, it is recognized that applied environmental research must address current problens; consequently, program priorities

may change during and after the five-year period. As a result, the program is

1 planned as a continuing program designed to address changing priorities.

TABLE 1. LEDO PROGRAM WORK UNITS

"Priority Work Unit Title

I Toxic Substances Bioaccumulation

and Biomagnification in Aquatic

Organisms

"2 Environmental Interpretation of

Consequences from Bioaccumulation

3 Efficiency of Capping in Reducing

Cumulative Effects of Dredged

Material Discharge

4 Techniques for Predicting

* Effiuent Quality of Diked

Containment Areas

5 Toxic Substances Bioaccumulation

in Plants

- 443

0
Program Objective

The principal objectives of LEDO are to provide new or improved technology to predict long-tenu (including cumulative) environmental impacts of

dredging operations and to address methods of minimizing any adverse impacts.

The technology will allow the CE to meet its dredging and regulatory missions

in a manner that is environm-nrtally sound while reducing or eliminating

"unneeded environmental constraints imposed on these activities by other regulatory agencies. Such technology is essential in the planning, design, construction, and operation of CE dredging projects as well as in evaluating per0 mitted activities. Study results will provide a valid technical basis for the

"Corps to continue to influence the direction of criteria and guideline development as well as resolving conflicts with other regulatory agencies. Inherent in the principal program objectives is that technology he provided in the

form of usable end products for all functional elements within the Civil Works

"area of the CE. Costs associated with the technologies will be presented. It

is also imperative that the results he presented in a manner such that continued credibility is maintained with other regulatory agencies and

environmental-awareness groups. Therefore, an emphasis will he placed on

"presenting research results in the technical and scientific literature while

ensuring results are immediately available to the field through normal CE

"channels.

"WORK AREA A: EFFECTS OF AQUATIC DISPOSAL

Three work units that address long-term effects in the aquatic environ-

"ment have been initiated at present. The following discussions present the

work unit, the progress to date, and the benefits hopefully derived. 1

'Work Unit I: Toxic Substances Bioaccumulation

and Biomagnification in Aquatic Organisms

The objective of this work unit is to develop predictive methods for

determining the rate and depree of bioaccumulation and blomagnification of

toxic substances from cont'iiinated dredged material by aquatic organisms.

This will be approached b determining rates and maximum levels of bioaccumulation and biomagnifica-ion of PCB's and other toxic substances from a variety

of types of dredged Trateriat. Biological techniques for use by CE field elements in predicting rates and levels of uptake will be evaluated and refined.

Chemical procedures for rapid prediction of rate and magnitude of bioaccumulation from sediment will he developed and assessed. In addition, the magnitude

of biomagnification will be determined in short food webs including benthic

and epibenthic aquatic organisms. Finally, the potential impact on ecological

"and human health will be evaluated.

The initial laboratory studies on rates and maximum levels of bioaccumuo lation reached when aquatic organisms are exposed to contaminated sediment

were conducted in FY 82. Species studied were freshwater clam Corbicula

fluminea and the freshwater crustacean Macrobrachuim rosenbergii. Concurrent

with these studies were investigations of rapid methods of predicting final

444

I

u I I
equilibrium bioaccumulation levels and -if the feasibility of predicting ulti-

* mate levels on the basis of short tests and geochemical analysis of the sediments. A comprehensive literature review on fooi web biomagnification in

aquatic organisms was begun and 'initial Laboratory biornagnification studies

*were conducted. These studies included a short food chain consisting of the

marine worm Neanthes arenaceodentata and the fish L~eiostomus xanthurus.

Fu ture investigations will he expanded to include a wider range of freshwater and saltwater species and dredged material. Species to be studied j include the freshwater minnow Pimephales pronelas, the freshwater crustacean

*Daphnia magna, the estuarine clam Rangia cuneata, the marine worm, Neanthes

*arenaceodentata and the estuarine crustacean Palaemonetes pugio. Investiga-

* tions of the ability to predict bioaccumulation from sediment characteristics

* will bre continued and the literature review on food web biomagnification will

* be completed.

In addition, contaminants which are most often accumulated will he identified and the level of accumulation of these contaminants will be correlated

with sediment characterization and interspecific differences. Finally, the

actual extent of bionagnification in aquatic food webs will be quantified and

related to the health of the contaminated organisms.

Work U'nit IT: Environmental Interpretation

of Conseque'ces from Bioaccumulation

The objective of this work unit is to develop and evaluate procedures P. r

*predictive interpretation of potential envirornmentail effects of bioaccumulation of toxic substances from dredged material by aquatic organisms. This U work unit ties very closely with Work Unit I in that it is essentially an

* interpretation of those findings.

The biological consequences of bioaccumulation will~be studied in aquatic

animals exposed to a variety of types of dredged material containing important

jiorganic and metallic contaminants. Correlations of bioaccumulation with biological parameters such as reproduction, growth, and developmental abnormal-

* ities will he determined in a variety of representative aquatic organisms.

The biological parameters selected for study will be promising first-generation

techniques which have not been developed, to the point where they are routinely

used. These parameters will be assessed in freshwater animals exclusively.

The magnitude of change in key parameters which causes deleterious effects to

the organisms w~ill be investigated and correlated to the degree of tissue con-

* taminiation. Through this approach, results of mandated bioaccumulation studies

cam be realistically interpreted in terms of potential for biological harm.

A comprehensive literature review has begun on the correlation of body

burden with biological effects and the consequences of those effects. Prelimi-

*inary findings of the review indicate that future efforts should concentrate

on the effects of halogenated 'hydrocarbons on the most sensitive infaunal and

epibenthic species. Those portions of the life cycle which appear partic-

* ularly vulnerable should, Le examined.

445

S!
, In the future, laboratory studies will he initiated to aid in the inter-

"pretation of consequences of bioacciimiitation based in part on the findings of

the literature review as well as newly generated "state-of-the-art" information. These studies will include chronic and acute effects of contaminated

sediments on the reproductive potential of benthic organisms. These organisms

include the freshwater flea Daphnia maa!, the marine worm Neanthes

arenaceodentata, and the estuarine grass shrimp Paiaemonetes pugio. In addition, methodologies will be developed and tested to determine the ecological

survival potential of most sensitive species. These invr-tigations will be

conducted so thait the degree of tissue contamination may be related to the

general overall health of aquatic organisms. This relation will he made in

light of the regulatory needs of the permitting process and of disposal

activities. In addition, the effects of bioaccumulation on the most sensitive

species and life stages will be continued and expanded to include additional

organisms and testing protocols. This information will be examined and

related to short-term bioassay/bioaccumulation studies currently in use by

field personnel.

Work Unit III: Efficiency of Capping in Reducing the

Cumulative Effects of Dredged Material Discharge

The oblective of this work unit is to evaluate the adequacy of predictive

"techniques for evaluating cumulative effects through onsite fieLd investigaStions. This will- be approached through field studies which will determine the

overall effects of disposal and aid in refining capability for predicting

environmental impacts. The environmental efficiency of capping contaminated

material with clean material will be determined. Routine dredging operations

will be modified so that similar portions of the dredged material are discharged at two separate points. One will be capped and the other uncapped.

Effects of the two discharges will he compared.

Six operations suitable for studying the effects of repetitious discharges and capping have been surveyed. In addition, numerous previous capping operations have been reviewed and critically analyzed to provide a sound

* scientific basis for this study.

In the future, one of the cooperative studies discussed earlier will he

selected and initiated with modifications as appropriate based on findings.

Disposal operation in which part of the material is capped and part is

uncapped will be conducted. Levels of specific contaminants in organisms

inhabiting both the capped and uncapped areas will be determined. This will

provide the basis for assessing the efficiency of capping.' Furthermore, the

movement of contaminants and bioaccumulation in key species at the capped and

uncapped sites will continue to be studied to determine long-term cap stability and effectiveness over time.

Benefits

Recent legislation requires the CE to assess long-term effects of dredged

material disposal on rederal and non-Federal dredging projects. However,

long-term effects of dredged material disposal are not well understood and

446

/&
this lack of understanding has resulted in costly delays on Federal and nonFederal projects and often in the imposition of questionable environmental

- constraints. The national emphasis onidevelopment of coal-exportLng facilities will increasc the number of major dredging projects. Lack of information

Q on long-term effects can significantly delay these project. since they are

subject to international agreements as welt as national environmental legislation. Efforts within this work area wilL provide guidance to the field for

assessing potential impacts and on methods of minimizing any adverse impacts

of the disposal of dredged material. Results of these studies are necessary

to permanently resolve current conflicts on specific major dredging projects

i where only interim resolutions have been reached with other regulatory agencies. In a recent meeting of a technical cormmittee of the London Dumping

Convention, the concept of capping as a mitigating measure for disposal of

"contaminated dredged material in the ocean was accepted contingent upon the

- re.ults of further research on the effectiveness of the method. In summary,

these studies are required in order for the CE to meet Congressionally marndatel requirements on assessing long-term impacts of dredged material disposal.

WORK AREA B: EFFECTS OF UPLAND DISPOSAL

Two work units that address long-term effects in the upland environment

" -have been initiated at present.

Work Unit IV: Techniques for Predicting Effluent

Quality _f Diked Containment Areas I

The objective of this work unit is to develop procedures for estimating

the level of contaminants in dredged malterial containment area effluents. The

research approach will involve both field and laboratory investigations. Confined disposal operations will be nonitored for conceptual development of lab-

"" orat.)ry tests for predicting effluent quality of containment areas. A compu- 7: tational procedure will then be developed for determining before-the-fact

requirements of the mixing zone. Veriflication of the developed procedures

:1 will be accomplished at several field s!ites under varying flow and operational

conditions.

A first-generation modified elutriate test has been developed in the laboratory using sediments from four disposal operations. In addition, preliminary field verification in support of the laboratory 4ork has been accomplished.

"Future research will involve fieldi verification of the modified elutriate

"test procedure to accurately simulate retention time, settling regime, and

other conditions within a disposal area!. Additionally, development of an

interim technique for prediction of contaminant levels in disposal area effluI ents will ie conducted. The technique will ,ise the modified elutriate test as

a basis and will account for transport of particulates and associated contaminants in the disposal area supernatant wters. Finally, sites for later field

verification of the predictive technique will be selected and predictive tests

for field verification will he carried out.

44

• 447
Work Unit V: Toxic Substances Bioaccumulation in Plants

The objective of this work unit is to develop taethods to deteriline bioaccumulation of toxic substances in plants on dredged material disposal sites.

The approach will initially involve determining the movement of toxic substances from dredged material into both freshwater and saltwate2r plants and

the level of bioaccumulation in the tissues. A variety of types of dredged

material will -e studied under both flooded and upland disposal environments.

A standardized plant bioassay predictive methodology will then be developed.

Results of the plant bioassay tests will be interrelated ta existing data

bases ot. toxic substances by plants through contracts with (1) the Institute

of Soil Fertility,, Haren, The Netherlands, for agronomic plants grown on contaminated Dutch sediments; (2) the Uiiversity College of Wales, Aberystwyth,

Wales, UK, for agronomic plants and --altmarsh plants grown on rietal mining

waste; (3) USDA Beltsville, MD, for agronomic plants grown on sewage sludge

amended soils; and (4) the Delta Institute of Hydrobiological Research,

Yerseke, The Netherlands, for saltwarsh plants grown on contaminated sediments. These contracts will substantially enhance the interpretation of plant

bioassay test results.

Tle purpose of these contracts will be to compare the WES data on plant

uptake of toxic s,,bstances by Cyperus esculentus to existing data fron other

researchers on other plant species in order to take advantage of previous

research results and to enhance the interpretation of the meening of plant

uptake data on dredged material.

In 1982, under Freshwater Bioassay Development, comparison of results of

laboratory tests to field tests were conducted, but were limited to specific

disposal sites. Plant uptake of toxic substances by Cyperus esculentus was

compared to other plant species in The Netherlands, Wales, and the Uuited

States.

In addition, development of laboratory procedures for a saltwater plant

bioassay ws initiated in 1982. Spartina alterniflora's growth and uptake of

toxic metals from mining waste contaminated sediments were compared in laboratory and field tests in Wales, UK.

Continued comparison of results from laboratory and field plant bioassay

testing is planned for the future. Comparison of plant uptake of toxic substances by Cyperus esculentus to agronomic crops grown on bLudge-amended soils

and complete plant bioassay testing of toxi- metal mining waste in Wales, UK,

will continue. Also, development of field test procedures will be updated as

needed.

In addition, development of the laboratory saltwater plant htoassay procedures will continue. The completion of the comparison of Laboratory and

field plant bioassay tests in Wales, UK, will oe supported by Dutch studies

comparing contaminant uptake by Soartina alteraiflora to other saLtmarsh

plants grown on contaminated sediments.

448
,÷ . it is planned that the freshwater plant bioassay will be available in 1985

- and the saltwater plant bioassay by 1986.

* Benefits

Effluent discharges from containment areas into waters of the United States

are legally defined as dredged material and conseque-tly are subject to the

Corps' Section .404 regulatory authority. These discharges are also subject to

more stringent State regulations. The containment areas are subjact tc the

National Environmental Policy Act and, in some instances, may be sublect to

the Resource Conservation and Recovery Act. These acts require evaluations of

impacts at or beyond the present state of knowledge. The results of studies

in this work area will allow the CE to make tne Congressionally mandated evalu-

. ations. The plant bioassays will allow for more sound decisions to be made

"*• regarding' disposal alternatives (e.g., aquatic, wetland, and terrestrial).

0

4

S

449

S
SPECIALIZED DREDGES DESIGN'ED FOR

BOTTOM SLDIMENT DREDGI(,;

Akihiro Kaneko

Yoshiharu Watari

Noriyoshi Aritomi

Japan Dredging and Reclamation

"Engineering Association

ABSTRACT

This paper describes the functions, characteristics, and turbidity prevention or controlling

effect of specialized dredges designed for bottom

sediment dredging and developed for exclusive

practical use.

In bottom sediment dredging, the prevention

or controlling of turbidity arising from tiO

0 dredging operation is an important problem.

When compared with cutter suction dredging,

the specialized dredges can significantly reduce

tile potential generation of turbidity.

I NT ROIUCT I oN

Since the late 1960's, Japan has made remarkable progress in

economy and industry.

As a result of coastal development and factory construction,

Sdt.terioration of tihe environmental conditions and hazardous pollution

"in water, air, noise, or vibration have frequently taken place. For

th.tse reasons, strict regulations and laws have been imposed on the

sources of pollit ion. One environmental goal is tile re~oval of sedimenits containiing toxic materials suich a% mercurv and 1'CH. a large

aroimit of oi l, or organic substances, and improvement of r.he water

* 'Itality.

Removal of tilth contamIinated sediment wotild improve- the qu1alit of

Oile W•'.etr. 1heretore, removal must be carried out without secondarv

ipolltitiioI likelv to .accompanv removing work. In the past, this hIas

b',tti diff icrilt to perform. Io solve this problem, we have develori•d a

""0 I- }SIlIR, an.ti-polluttion d red ginsz sv-stem, hbr•-ed on tihe Conventiotnaill

cr trr oic.t ion dredge , and . rr performinv. sediment remolving: works tisins.r

t hi L etm.

450

0.
- When compared with the conventional suction dredging, the REFRESHER anti-

. pollution dredging system has accomplished the specified purpose of preventing

secondary pollution.

FUNCTIONS NECESSARY FOR BOTTOM SEDIMENT DREIX;ES

Almost all dredging works to date have been conducted for land reclamation

and deepening and maintaining navigation channels and anchorages for increasing

traffic and safety.

However, bottom sediment dredging is intended to improve water quality

and therefore must be undertaken without causing secondary pollution. Bottom

.* sedinents are thin layers with high water contents containing silt, clay,

debris, and other organic substances as well as toxic materials.

lherefore,. for specialized dredges to dredge bottom sediments with

safetv, within a short period of time, and in an economical way they must

provide thle following functions:

a. fhe dredge must fully and completely remove bottom sediments

and prevt.nt generation of turbidity. Although we want to

prevent the ,euneration and dispersion of turbidity arising

* from dredgir:g, we must examine the factors contributing

to tile .eneration of turbidity in the conventional cutter

suction dredles:

(I) lurbiditi; arising from the cutter suction dedrjno_0eration.

As the cutter used for dredging sandy materials and conveying in the suction mouth is rotating, the materials not

taken Into the suction mouth are scattered. Figure I shows

the cutter used for the model test and the turbidity

arising with cutter operating4 at a low speed. This turbidity occurred frequently at the rear side of the cutter

and stay'ed along the cuts or windrows.

*71

* F gtre I. Dredging experiment by cutter model

431
(2) Turbidity arising from installation and reinstallation of anchors

and spuds. Dispersion and agitation of dredged sandy materials

take place when the anchors and spuds are installed/reinstalled.

(3) Turbidity arising from the maneuver of dredges. Silty/clayey

materials attached to the wires of dredges are scattered when

the swing wires are used for swinging right and left and the

anchoring wires for smooth shifting are set.

(.4) ~iirbiditv cauised bv the lower inart of the ladder head when

d r~edging is conducted in shallow waters and/or in thick layers.

While gaining access to the bed point, the ladder head causes

water currents that scatter the dredged material,. thereby causing turbidity.

Of these four factors, factors (2) and (3) are disregarded due to

nej.ligible turbidity generation. However, factors (1) and (4) are

considered influential. Iherefore, measures to prevent turbidity

4entvration shall be focused on the turbidity arising from the cutter

suction dredging operation and turbidity caused by the ladder head.

oCplete removal of bottom sediments is necessary. Sandy materials

excaivated bv. the cutter are conveyed into the suction mouth. As the

l.a,idcr ,tn.le (the dredging depth) increases, the suction mouth positi,)u blcornms higher from the sea bottom and all of the sandy material.s irte untt conveyed to the suction mouth and part of the material

is L,.zett red behind ,the cutter.' When dredging in thin layers,

s.ch .as in b,)ttom sediments, additional excavation is necessary to

obtain tLhe rev(iired depth and, therefore, an additional volume of

dr.2dgin_-, is inevitable. For the dredging of the bottom sediments,

the, minimum volume of additional dredging is required to conduct the

compltu removal of the designed dredging materials to increase

v. f icienc'; in transport and disposal of the bottom sediments.

U. hie dredve must excavate the bottom sediments in high concentration.

When dre~dging thin layers of the bottom sediments by cutter suction

drt-dz._,, the siction mechanism takes in surplus water and has a low

mud concentration. When placing bottom sediments at the disposal

arvvi, le.s spill wat,'-r is preferable because of the difficulty in

scuring disposal area-i. Therefore, high concentration dredging is

pr,. teranle.

(Copetent optration )f the dredges is necessary. Operators o~f

ru..s :nmust prevent ,eueration and dispersion of the bottom sediim.ots and :-,,t drdge in ýi, ih concentration. Though dredges can

;r.'vile ti' ab.,w'-h,!,cribvd functions, they do not necessarily do so

becatise o .f 1,tcnii. I topo,,raphical, or operating conditions.

,roors er., ust confirm,' while dredging, that the generation

ml Ii di,;siun )Of turbidity are prevented and that the bottom sediments

Atr, cCW::Ictely removed. Ti addition, operators must understand the

prop,,r thickness of the bottom ,edimcnts to be dredged, and must

eliW!'iii A hi Ji Conccent ration, proper swing speed, and other optimal

O)Perat inj conditions.

$'52
CHARACTERISTICS OF THE REFRESHER ANTI-POLLUTION DREDGING SYSTEM

Functions

Figure 2 and the following paragraphs show a concept of the REFRESHER

which provides the functions necessary for dredging the bottom sediments.

Pipe.

*krv C6,,w ja" i torwo SIM fWr Wb.AV "4-A"M

In 1drpdr

Sihip pu.mp, (6w .~d,

C" Q-r %aiý' L"*

- Ij

(avber Undead-e

Figure 2. Concept at REFRESHER system

a. Prevention of turbidity and complete removal of the bottom sediments.

Prevention of turbidity

(1 Gather head (see Figure 3)

The gather head is a ribbon blade with a reducing spiral at the

front end. It causes less scattering by centrifugal force of

sand, and collects the sand in the suction side while cutting a

variety of earth, from soft mud to hard ground. Revolution of

* gather head is convertible to cope with the property of the

earth to be dredged, the dredging thickness, and the swing

Speed.

453
II

°...

£ Figure . aciier ;,Ead

(2) Cover and shutter

Figure 4 shows a front and side jiew of the special mud collector.

As shown in the figure, the cover which completely conceals the

-gather head has a shutter adjustable to open or shut by an adjuster

plate for suction water and is structured such that it does not

leak any turbidity generated by dredging.

(3) Check vaive, gas collector, and other equipment

Check valves at the suction and discharge side of the pump prevent the back flow ot the sediment water into discharge pipes in

. an emergency. [he gas collector apparatus (shown in Figures 2

and 4) collects the gas produced while dredging and delivers

the gas to the suction pipe.

Complete removal of the bottom sediments

(1) Position controller (Figure 5)

Yhe position controller controls the revolution loci of the

gather head to the angle parallel to the ground and. to control

this angle to meet the dredging depth and will attain the complete dredging without any sediment residue. Moreovur, in this

* case, the maximum prevention of sediment dispersion will be

attained and condition of dredged loci will have no wave typtes

witlh a less excavation surplus after dredging.

454

I
Underwater Underwater TV camiera

TV camera Turbidisensor Monitor plate

Hydraulic 7

cy Ii nd-r

Gas or folec Sutter

\Suctine conltrol plate

Gather head

Gather head

Ssing direction \ hte Ruhherý plate' Sht

(a) Front view ()Side view

Figure 4. Special mud collector

Turbidimeter

Uubdndeerwae Vcmr

Underwater TV camera

N, Monitor plate

(h) Shallpwdredging (-30.5m)

Figure5. Anle adTuridiment b oit onrle

Unewtr Vcmr

45/- oitrplt

Suto lde
b. High concentration dredging

(1) Ladder pump and ship pump

A centrifugal pump is provided at the ladder to conduct suction

of the sediments in high concentration. In addition, a ship

pump is used in combination for discharging dredged sediments

for a long distance. A series operation of ladder pump and

ship pump will be able to discharge the dredged material about

3000 m.

(2) Cover, shutter, and other equipment

Cover, shutter, suction control plate, position controller, etc.,

help prevent excess water in high concentration dredging.

c. Operation monitoring

Monitoring turbidity

(1) Monitoring by underwater TV camera

An underwater TV camera is installed at the top of the cover;

operators can observe the turbidity conditions above the head

4. at any time from the monitor in the operation room. The system

consists of an underwater camera, a monitor TV video system, and

a recording of the date on the picture. Figure 6 shows a

monitor and video system in the operation room.

(2) Monitoring by turbidimeter

The picture on the monitor cannot indicate the extent of turbidity

quantitatively. Therefore, a sensor or turbidimeter is set at

the same point as the TV camera and operators can observe the

turbidity conditions by monitoring the TV and its extent by the

turbidimeter.

Understanding operating conditions

(1) Dredging depth meter

To understand the correct water depth before and after dredging,

sets of a transmitter and a receiver of the echo sounder

are installed at both sides of the cover. As the measured

result is indicated and recorded in the operating room, the

operator can promptly find the dredging depth, dredging earth

thickness, and operation conditions, and can ensure that the

dredging is fully completed to the required thickness (see

Figure 6).

456

4
Figure 6. Monitor TV and echo sounding recorder

I !ranspI.ta~t~io~n_ eho

In the REFRESHER sys;tem, two transportation methods are available: barge

loading and pipel ine (see Fijaure 7).

At present, the REFRESHER system dredges are: REFRESHER No. 6 Fuyo;

- ~ REFRESHER No. 3, and M-IN -REFRESHER Tokyo Maru. The former two dredges are sultaile r redinylare-to mdu-scale work such as a large amount of

sed imýen L'promptlv depos-ited over the wide ranee,; the MTNI-REFRESHER Iokvo

MIain isý a portable drteduet su table for small-scale work in narrow areas.

457
Ladder pump ~

(a) Barge loading method

- ship pump

* Ladder pump

(b) Pipeline method

Figure 7. Transportation methods

S-puci fications

Various characteristics of thle REFRESHER system have been described.

Givenl below arE thle main specifications; Figure 8 gives the general arrangement

of REFRESHER No. 3 for easier reference.

Genural items

Dredoing4 depth: 3.5 to 20.0 m Discharge distance: Barge loading, 3000 m 0 1red-ging capaci ty: 150-400 m3/hr

b1ill dimensions:. L. 45. 60 m x8. 13. 50 m D. 3. 30 m 1)1 splaCUMen t at full load: 1200 tons

iOraft at full load: 2.20 M

Spec ial Mild collector

MIud collector drive unit: D)C 100 kw, 3-15 rpm

Shut ter: Hy-draulically remote control

1'o- it ion controller:

Ga~s collector: Ejecter system

45
,41*

AL LIIý -~

C3/

FIR; 11

'S -459
Dredging pump

Ladder pump Ship pump

Type Centrifugal Centrifugal

Nominal shaft 150 PS 1800 PS

Horsepower 3 3

Capacity 800 to 2000 m /hr 800 to 2000 m /hr

Total head 10 to 20 m 20 to 50 m

Rpm 490 to 700 200 to 310

Prime mover AC 110 kw D 2000 PS

Frequency conversion) (Diesel engine)

control

Suction pipe dia./Discharge pipe dia. 40OA/400A

Suction check valve, change over valve

Operation monitoring system

Underwater monitoring TV: Underwater TV camera, monitoring

video, light

Turbidity monitoring: Underwater turbidimeter

Dredging depth meter: Echo sounder

TURBIDITY PREVENTION BY REFRESHER SYSTEM DREDGES

The REFRESHER anti-pollution dredging system was developed for practical

use in preventing turbidity arising from dredging. Illustrated and explained

below are the results of our investigation into the turbidity around ladder

heads of conventional cutter suction dredges and REFRESHER dredges.

Turbidity by Cutter Suction Dredges

The dredging work in Port Y (see reference 1) involves dredging of an

anchorage area (10 m deep, about 135,000 m2 in dredging area, and about

530,000 m3 in dredging volume) by means of cutterless suction dredging (without the cutter) of 1.i- to 1.7-m-thick upper layers of soft clays and cutter

suction dredging of 1.9- to 3.0-m-chick lower layer (Figures 9 and 10).

4h

1' -

Figure 9. Cutterless suction dredging

460

/
Figure 10. Cutter suctior dredging

Stated below are the particulars of the dredge, physical properties of

the dredged material, operation conditions, and investigation results of the

turbidity.

Major Specifications of the Dredge No. 6 Fuyo

General items

Hull dimensions: L.53.68 m x B.14.00 m x D.3.81 m

Displacement at full load: 1880 tons

Draft at full load: 2.74 m

Discharge distance: 5000 m

Dredging capacity: 200 to 1300 m 3/hr

(Mud concentration of more than 30%)

Dredging depth: 6 to 21 m Dredging pump: Prime mover: F.P. Gas Turbine (Nominal) 4000 PS

Physical Propertiez of Dredged Material

Specific -ravitv: 2.63 - 2.70

(;rain-size distri!bution

Upper: Silty clay (Partly about 15% sand

inclusive)

Lower: Silty clay (Partly about 50L, of sand',

gravel inclusive)

et density

Upper: 1.25 - 1.40]-!cm3

Lower: 1.50 - g/cm

461

• A - .- .
Operating Conditions

Table 1 indicates the operation conditions of the cutterless suction

dredging (for upper layers) and the cutter suction dredging (for lower layers)

Table 1. Operating conditions (I1

Cutterless suction dredging Cutter suction dredging

(upper layer) (lower layer)

Swing speed (m/min) 5 - 10 5 - 10

Cutter rpm 15

Dredging thickness (m) 0.5 - 1.0 0.6 - 1.0

Spud moving aterval (m) 1.5 - 2.0 2.0

Flow rate in pipe (a/sec) 4.3 - 4.8 3.5 - 4.5

Note: Diameter of discharge pipe: 670 mm

Turbidity Investigation Details and Results

To comprehend the scope and extent of turbidity around the ladder head,

turbidity and visibility were measured in seawater pumped up by a simple

automatic sampler and obtained from the positions shown in Figure 11.

To comprehend the influence around the dredge, measurement of turbidity

and visibility was made in the seawater at the points shown in Figure 12.

Since the relation SS (Suspended Solids) = 1.7 x Tb (Turbidity) was obtained,

the turbidity is to be expressed hereafter by the conversion basis of SS.

A Cutterless (A)F Cutt"

~• L )D () u~la

C' Q

F Cutterless -0-i 1 *

Figure 11. Checking position of ladder head for

cutterless suction dredging and

cutter suction dredging

462
b

IO,

Figure 12. Measurement points around dredge

The highest velocity of the curren, during the surveying period was only

about 5 cm/sec, not enough to cause any influence.

The investigation results are summar.zed below.

Swing speed, rpm of the cutter, dredging thickness, etc., of every item

of the operation conditions greatly affect turbidity generation during cutterless suction dredging. Figure 1 3 shows the relation between the dredging

thickness and SS at the time of the cutterless suction dredging. Note that

the larger the dredging thickness, the more the SS increases.

.C

300" D F., -IG- 0 A V ,

A, 0.5-- LI. '

I 00t , A

"2 "A 

-0,3 -0.5m . , A

/

'I

010.

(A) 'B) C (D) E F G; H

Measurement point

•Fi-, I I. , elation h,,,twe. 2n dr, din," thiicknes,; and SS

(cuttcrless suctic,i drediinv,)

463
4

Swing speed, swing direction, etc., were not found to influence turbidity

during cutter suction dredging. Figure 14 shows the average SS values at

respective measuring points during cutterless suction dredging and cutter suction dredging. lurbidity during cutterless suction dredging was almost half

that of cutter suction dredging.

L AF Cdta,. S

('utter surtim

dirudging /

* F 'x

A \

da u eutt ind

.~ dredotini

AA

fAi B C 1)) K F G H

Me~asureme.nt point

Figure 14. Comparison in SS of ladder heads between cutter suc~tion

dredging and cutterless suction dredging

Figure 15 shows turbidity in areas and in degrees during cutter suction

dredging. According to Figure 15, when turbidity from cutter suction dredging

falls to 5 m < 10 m, turbidity iii degrees averages 100 to 200 mg/l SS. If

continuous generation of 100 to 200 mg/l turbid water is assumed 4ithin this

area, the turbidity is generated at a rate of 500 T 3 /min ( 5 m x

10 in lO m/min) for a swing speed of 10 m/min.

464
I- .[Portside in bracket .Unit; SS "mg/t

H 10/. 104 75p --

126 - ' • 121 >

253 BG * $ E

ann

241 " , /

291 I)E--" /

10 . . M - .

7.O.rm 3.Om -

Figure 15. lurbidijv in areas and in degrees by cutter

suction dredging, i'ortside in bracket

'Unit: mS, rg/'

2 indicates tuie. net contents ot the turbidity generation, taking

into c,,nsideration the operation conditions and the dredging volume during

cutter •,'ction dredtL•inu.. ,About 5 tons ,f turbidity per hour is generated.

Most o; Ltiey ,wucrat n turbidvitt, however, * ettles to the sea bottom.

}hle 2. Net ~iuntsoutT turiidity genert ion (cutter dredging) (1)

uruiditvM Min/fir turhidity D)redcin4 Net contents of

-'rn,' spet-d araI ,w. razv taunerat ion volknlm turhidity' genera-

- 1:uiu (:n-) S.S (tmgil) i t hr (mr /hr) tion (t /m3

11J 200)

35) U. 10 5.19 hOO 8 - ji)-3

V'i.-r,: I6 is the restilt of mcasurement of the turbidit. around the dredge.

1he. (i;,ure slkov's th;at, althoujit the t uirbiditv is obs-,&rved 1t points 7 i (;ea

o))t ton -P) :n) below water level, the turhiditv is much smaller than around

0 tLhke laidher head. ,'nothter investi'gation conducted at a ro:n. t 1' 1in1t r(veatled

tiat tthe inflhunceý over tirbidity is nearly nonexistent over 1)0 m- bevn'id thei

d r,.d :. .

465
II A4- oz-ý

A 7.Om below water / 14'- - level (cutter dreding

12. A.,,\ / /

=/ /

S 10.

•1, 7.O re W ~ow water Z J

level ,cutterless dredanmw

" e.li below. water

eve rlevel dcutterless dredlin#

& /

5 -- -- - 0~. -.... __

0.5m below water

4 level (cutterless dredxins)

af

Measurement point

Figure 16. lurbidity around dredge

r, _ REFRESHER dredge (1I Ba,)

, 2

Bottom sediment dred-inc work in T Bay involved about 300,000 m in

drudging area and about 150,t)OU) m3 in dredginý4 volume. The REFRESHER system

"- *has dredged the bottom sediments in about half the designated area, transported

by means of pipelitles to the disposal area.

Major Specifications of the Dredge REFRStHER No. 6 Fuyo

General i tems

Hull dimensior ;: L.53.68 m B.14.00 m x D.3.81 m

Displacement of full load: 1880 tons

Draft at full load: 2.74 m

0

•:Q 466
Discharge distance: Barge loading - 5000 m

Dredging capacity: 200 to 1,300 m /hr

Dredging depth: 6 to 21 m

Dredging pump

Ladder pump Ship pump

Type: Axial flow Centrifugal

Nominal shaft:

Horsepower: 200 PS 3600 PS

Capacity: 700 to 5000 m 3/hr 700 to 5000 m 3/hr

Total head: 4 to 7 m 10 to 100 m

Operation monitoring system

Same as REFRESHER No. 3

Physical Properties of Dredged Material

Physical properties of the dredged material are indicated in Table 3.

l'he dredged material is sandy silt.

Table 3. Physical properties of dredged material (1)

.. train-size distribution (%) Natural

Specific gravity water content Wet density

Sand Silt Clay (%) (g/cm3)

2.68 - i.80 7 - 19 65 - 75 10 - 18 146 1.30 - 1.32

operating Conditions

0. Table 4 indicates the operating conditions.

Table 4. Operating conditions (2)

Dredging Spud moving Dredging Flow rate

Swing speed Gather head thickness interval depth in pipe

S(m/min) rpm (m) (m) (m) (m/set)

5 - 10 3 0.4 - 0.8 2.5 7.0 - 9.0 3.0

* Note: Diameter of discharge pipe: 610 mm

•'urbidity Tnvestigation Details and Results

PTo comprehend the scope and extent of turbidity around the ladder head,

turbidity was measured by installation of the turbidisensor at the phases

shown in Figure 17. The turbidity measured at points 0.5, 2.0, and 5.0 m

* below the water level are shown in Figure 18. The turbidity was measured at

. points I through 9 at three different depths.

467
.- abrat 4.5m- about 4.5m- -2.0m- 2.0m-

--B B

•.Swing directmion

(a) Front view ()ieve

Figure 17. Checking position of ladder he

S50Orem 50.Oe ... 1

3., 4. • -

E

EE

98 A

Swn- Dreding width

Figure 18. Measurement points around dredge

_ Tfhe relation SS =1.5 Tb was obtained and the curren= at the highes.

4 spet~d d•:rin• the surveying period was about 10 cm/sec. Figiire 19 shows the

relation between the swing speed and the turbidity at point iC of the ladder

head. It waas found that the more the swing speed increased, the larger the

degree of turbidity became and that the degrees of turbidity were less than

* a few mg/i at a swing speed of 5 rn/min and around 20 mg/i a~ 10 n/min.

468

IE
,- Average SS

- Maximum SS

80fo I 60i

•~~r -,,/16-"

06

00

00

soo

20ý

E 0 ... 0 0o .. .. . .

10 09

Swing speed Vs rm/min)

Fi-ure 19. Relation between swing speed and turbidity at point C

Figure 20 shows the relation between swing speed and finish performance

(tihe di ffurence between the actual finished depth and the assumed finish depth).

When the swing speed is slow, the actual finished depth becomes deeper than

the assumed finish depth (in case of a swing speed of 5 m/min, the actual

finished depth is about 0.3 m deeper than the assumed finish depth); as the

suction efficiency is good, there is little turbidity generation. However,

mud sediment concentration is lower due to suction of excess water.

On the other hand, the more the swing speed increases, the less the

actual finished depth (about 0.1 m for 10 m/min); as the suction efficiency

worsens, the more turbidity is generated.

I 4

j. 46

" "'
I

. Maximum t

0 Minimum t

- 0.6 Gather head r.p.m 3-5r.p.m

Seabed level: -6.0 m mlw

0.5

s.- 0.4

0.3 0

,. " 0.3

S0.1. 00.0

C -0

2 4 6 8 10 12 14 16

:.•: Swing speed m/rain.

SFigure 20. Relation between swing speed and finish performance

(difference between actual finished depth and assumed

finish depth)

,'-Figure 21 shows the average SS and the turbidity area, obtained from

S"measuring turbidity from points A to E. The SS value is much smaller than

•, that of cutter suction dredging.

='-Swing speed Sn/rain

::]Swing speed 10Sm/mm,

* 5 m/min -0.5 B

10 m/min-,42)

'- • --" '-2.7, 19I + 4. 5• 22 , l.1 213 1 o io E

4.Om . . ... 5.0m - -

* Figure 21. Average SS and turbidity area (1)

"470

6
=S-wing speed 4m/min

"-'Swing speed 8m/ain

-. 7 ,4m/min Bo

ri

E.O

Figure 23. Average SS and turbidity area (2)

T Table 8 indicates net contents of turbidity generation, taking into consideration the operation conditions and the dredging volume. The values were

0.01 t/hr at a swing speed of 4 m/min and 0.15 t/hr at 8 m/min, slightly

larger than the values found at T Bay.

Table 8. Net. contents of turbidity generation

Net contents of Swing Turbidity Average Min/Hr turbidity generation Dredging turbidity

* speed area SS volume

(mrmin) (in2 ) (mg/i) (t/min) (t/hr) (m3 /hr) generation

(t/m3)

4 14 4.2 2.35 x 10- 0 011 144 0.08 x 10-

24.5 19.1 3.74 x 10-3 0.150 240 0.63 x 10-3

Figure 24 shows the measurement results of turbidity around the dredge.

-* L'he changing values of SS are based on the elapse of time at measurement

points 4, 5, and 6 on the downstream side of the currents. Since all SS

values were smaller than tie value prior to dredging, no influence by dredging

operation can be observed.

e

,-473
"-0- Upper layer (-Irm) -- Intermediate layer (-7m) --- Lower layer (+ lm above seabed)

Measurement point 4

1 o0

Measurement point 5

1 10

E

01

1g Measurement point 6

A- - 2- ý=----

- C Pre- 30min. 1.5hr 2.Shr 1.Ohr

dredging after after after completion of

dredging dredging dredging dredging

Figure 24. Turbidity around dredge (2)

Table 9 indicates the results of the dredging efficiency; the apparent

* mud concentration is 28%.

Table 9. Dredging efficiency

Dredging Dredging Total Total Total volume per volume per Apparent

operating dredging Total dis- dredging operating dredging mud

time time charge 3 volume volume hour hour concentra- (hr) (hr) (m) (m3) (m3/hr) (m3/hr) tion (Z)

95.0 59.42 69,118 19,320 203 325 28

474

,
WORK EXPERIENCES

Table 10 outlines work experiences of REFRESHER dredges for reference.

Table 10. Work experiences of REFRESHER dredges

Dredging Dredging

Time for Volume area

Name of work completion (m3 ) (M3 ) Particulars of work

Bottom sediment Dec 1976 Dredged, pipelined for

dredging work to 104,390 143,000 1365 m and discharged by

in T Bay Mar 1977 spreading outlet installed

pontoon

Dredging work F.Y. 1980 Employed REFRESHER No. 3.

in M Bay to 14,790 23,456 Dredged and transported by

F.Y. 1981 a 2200-m3 sand barge for

a distance of 10 km to

dumping area

Dredging work June 1981 Employed REFRESHER No. 3.

in Port Y to '29,720 161,000 Dredge,, transported 7.4 km

Sep 1981 by 1900-m 3 sand barge and

unloaded by 1350-PS

unloader

Dredging work F.Y. 1977 Employed MINI-REFRESHER

in Port T to ;75,980 158,170 Tokyo Maru. Dredged,

F.Y. 1982 transported 8.5/13 km

by 200.1400 m3 sand barges

and unloaded by 250-PS

unloader

4

i.7

.'..
CONCLUSIONS

Table 11 summarizes the comparison of turbidity generation between cutter

suction dredging and REFRESHER dredging. Disregarding the slight difference in

physical properties of the dredged material, turbidity generation per hour was

about 5 tons by cutter suction dredging and about 0.01 to 0.1 ton by REFRESHER

dredging. Therefore, turbidity generation arising from REFRESHER dredging is

about 1/50 of that from cutter suction dredging under any circumstances.

The REFRESHER dredging system has thecapability to prevent the generation of turbidity. However, some allowance should be given to the REFRESHER dredging, when considering dredging efficiency.

- Table 11. Comparison of turbidity generation between cutter suction

dredging and REFRESHER dredging

Min/Hr turbdity Dredg- Net contents

Swing Turbidity Average generation ing of turbidity

speed area SS volume generation

Item (m/min) (m2 ) (mg/l) (t/min) (t/hr) (m3 /hr) (t/m 3 )

Cutter 10 200 0 10 5.19 600 8 x 10-3 "suction (5-10) 50 (100-200)

REFRESHER 5 14 4.5 3.15 x 10-4 0.011 273 0.04 x 10-3

dredging 3

"in T Bay 10 17.5 23.3 4.08 x 10 0.107 393 0.27 x 10

REFRESHER 4 14 4.2 2.35 x 10-4 0.011 144 0.08 x 10-3

dredging

in M Bay 8 24.5 19.1 3.74 x 10- 0.150 240 0.63 x 10-

REFERENCES

1) Takuji Nakano, Akira Onishi, Tomiyasu Kawazu: "Turbidity generation

arising from dredging works and on engineering methods attempting its

decrement." In: Proc. 30th Annual Conference of the Japan Society

of Civil Engineers. 2, 1975, pp 108-109.

2) Osamu Nakai: "Turbidity generated by dredging projects." In: Proc.

I'hird US/Japan Expkrts' Meeting.

476

/ [ //

"' //

I / l