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Management of Bottom Sediments

Containing Toxic Substances

Proceedings of the 14th US/Japan Experts Meeting

27 February-1 March 1990

Yokohama, Japan

Thomas R. Patin, Editor

92 4 24 20 ?

92 4 22 101 92-10380

March 1992 lll!llllIllhIlIlllillllll'Il
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Management of Bottom Sediments Containing Toxic Substances:

Proceedings of the 14th US/Japan Experts Meeting

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Thomas R. Patin, Editor

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13. ABSTRACT (Maximum 200 words)

The 14th US/Japan Meeting on Management of Bottom Sediments Containing Toxic Substances was

held 27 February - 1 March 1990 in Yokohama, Japan. The meeting is held annually through an agreement

with the US Army Corps of Engineers and the Japanese Ministry of Transport to provide a forum for presentation of papers and in-depth discussions on drdging and disposal of comtaniinated sediment.

14. SUBJECT TERMS 15. NUMBER OF PAGES

300

Dredging Sedimentation 16. PRICE CODE

Marine deposits Toxicology

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PREFACE

The 14th US/Japan Experts Meeting on Management of Bottom Sediments Containing Toxic Substances was held 27 February-I March 1990 in Yokohama, Japan.

The meeting is held annually through an agreement with the US Army Corps of

Engineers and the Japanese Ministry of Transport to provide a forum for presentation of papers and in-depth discussions on dredging and disposal of contaminated sediment.

Mr. Jimmy F. Bates, Chief of the Policy and Planning Division, Directorate of Civil Works, US Army Corps of Engineers, was the US Chairman.

Mr. Takashi Hashikawa, Director of the Envirorent Division, Ports and

Harbours Bureau, Ministry of Transport, was the Japanese Chairman.

Coordinator of the organizational activities and editor of this report

was Mr. Thomas R. Patin, Program Manager, Dredging Operations Technical Support (DOTS) Program, US Army Engineer Waterways Experiment Station (WES).

Miss Phyllis Davis, contractor editor for the WES Information Technology Laboratory (ITL), and Mrs. Jessica Ruff, ITL editor, were responsible for editing

and coordinating the text for publication. Dr. Robert M. Engler was Program

Manager of the Environmental Effects of Dredging Programs, of which the DOTS

Program is a part.

A, e~i iFor

D'i T & e ai

"i '' mmmn • i airBiN IN i 'XN _
CONTENTS

Page

PREFACE ............. ................................ i

ATTENDEES ............. ............................... . iv

AGENDA ............. ................................ vi

JOINT COMMUNIQUE ........... ........................... ix

OVERVIEW OF SIGNIFICANT ISSUES AND TRENDS IN THE

US DREDGING PROGRAM by J. F. Bates ...... ................. 1

MERCURY-CONTAMINATED SEDIMENT DISPOSAL WORK IN MINAMATA BAY

by M. Hirose and A. Yamaguchi ........... .................... 6

RESTORATION OF LAKE SHIBAYAMA

by M. Nakamura ........... ........................... 26

A PILOT STUDY OF DREDGING AND DISPOSAL ALTERNATIVES FOR THE

NEW BEDFORD HARBOR, MASSACHUSETTS, SUPERFUND SITE

by M. J. Otis ........... ............................ 38

DEVELOPMENT OF THE HIGH-RATE DEWATERING SYSTEM OF BOTTOM

SEDIMENTS AND WATER BLOOMS by Z. Yoshino, R. Sudo,

M. Watanabe, H. Misumi, S. Horiuchi, H. Okajima,

A. Yagi, and Y. Nishikama ........ ...................... . 50

EXAMPLE OF LATEST TECHNIQUES FOR BOTTOM SLUDGE DREDGING

by J. Hamasuna ........... ........................... 61

AN UPDATE OF DREDGED MATERIAL CAPPING EXPERIENCES IN THE

UNITED STATES by M. R. Palermo ....... ................... .. 73

TREATMENT OF DREDGED SLUDGE BY MECHANICAL DEHYDRATION

by T. Maekawa ........... ............................ 83

INVESTIGATION ON RESUSPENSION OF RIVER SEDIMENTS USING

THE ANNULAR FLUME DURING RAINFALL by K. Nikaido .. ........... . 114

HOPPER DREDGES APPLIED TO THE ALASKA OIL SPILL, MARCH 1989

by K. H. Patterson and J. F. Redlinger .... ............... . 131

INFLUENCE OF ANOXIC WATER IN TOKYO BAY AND ITS MANAGEMENT

PLANNING by J. Iwakami, H. Fuse, and H. Matsui .. ........... . 145

PROPOSAL OF THE SEA-BLUE PROGRAM--APPLICATION OF NATURAL

ENERGIES AND BIOLOGICAL ACTIVITIES TO WATER QUALITY

IMPROVEMENT ALONG COAST by Y. Hosokawa and T. Horie .......... ... 167

ii
Page

THE PROBLEM OF DIOXIN CONTAMINATION IN SEDIMENTS OF THE PORT

OF NEW YORK AND NEW JERSEY by J. F. Tavolaro and E. A. Stern . . . . 180

NEW SOIL STABILIZER FROM THE COMBINATION OF INDUSTRIAL WASTE

by M. Kamon and S. Nontananandh ....... .................... .. 191

DEVELOPING SEDIMENT QUALITY STANDARDS: COMPREHENSIVE SEDIMENT

MANAGEMENT IN PUGET SOUND by C. C. Krueger ... ............. . 207

SOLIDIFICATION TECHNIQUES FOR DREDGED BOTTOM SEDIMENTS

by N. Wada ........... ............................. 223

DEVELOPMENT OF A VACUUM CONSOLIDATION METHOD EMPLOYING

HORIZONTAL DRAINS by T. Chiba, H. Shinsha, and Y. Tani ....... .. 238

TOXICOLOGICAL ASSESSMENT OF HAZARDOUS WASTE SITES

by S. A. Peterson .......... .......................... . 260

FOLLOW-UP INVESTIGATION OF MARINE LIFE AROUND ARTIFICIAL

SANDY BEACH OF YOKOHAMA MARINE PARK AND PROBLEMS

CONCERNING THE MAINTENANCE AND MANAGEMENT OF THE BEACH

by T. Tanaka ........... ............................ 272

iii
ATTENDEES

14th US/JAPAN EXPERTS MEETING ON MANAGEMENT OF BOTTOM

SEDIMENTS CONTAINING TOXIC SUBSTANCES

US Delegation

Jimmy F. Bates Chief, Policy and Planning Division,

Co-Chairman Directorate of Civil Works, US Army

Corps of Engineers

Mark J. Otis Supervisory Civil Engineer, US Army

Engineer Division, New England

Michael R. Palermo Research Civil Engineer, US Army Engineer

Waterways Experiment Station

Jacob F. Redlinger Civil Engineer, US Engineer Division,

North Pacific

John F. Tavolaro Chief, Water Quality Compliance Branch,

US Army Engineer District, New York

Catherine C. Krueger Chief, Hazardous Waste Program Section,

US Environmental Protection Agency,

Region 10

Spencer A. Peterson Regional Scientist, US Environmental

Protection Agency, Region 10

Japanese Delegation

Takashi Hashikawa Director, Environment Division, Ports and

Co-Chairman Harbours Bureau, Ministry of Transport

Mitsugu Kawada Environment Division, Ports and Harbours

Bureau, Ministry of Transport

Munekazu Hirose Kumamoto Port Construction Office,

Ministry of Transport

Masaharu Nakamura Japan Sediments Management Association

Tatsunorl Kosaka Kansai International Airport Company, Ltd.

Zen-ya Yoshino Tokyo Science University

Jun-ichi Hamasuna Chairman of Technical Committee, Japan

Sediments Management Association

iv
Takeo Maekawa Japan Dredging and Reclamation Engineering

Association

Kiyoshi Nikaido Japan Sediments Management Association

Yasuyuki Nakayama Nagoya Port Construction Office, Ministry

of Transport

Hazime Matsui Second District Port Construction

Bureau, Ministry of Transport

Yasushi Hosokawa Port and Harbour Research Institute,

Ministry of Transport

Masashi Kamon Department of Civil Engineering,

Kyoto University

Nobuaki Wada Japan Sediments Management Association

Takeshi Chiba Japan Dredging and Reclamation Engineering

Association

Tsuneyoshi Tanaka Port and Harbour Bureau, Yokohama City

Kiyoyasu Mikanagi Ceneral Director, Ports and Harbours

Bureau, Ministry of Transport

Hisato Yamada Director, Second District Port

Construction Bureau

Koh-Ichirou Miyahara Vice-Mayor, Yokohama City

Wataru Kitamura Director, Port and Harbour Bureau,

Yokohama City

V
AGENDA

14th US/JAPAN EXPERTS MEETING ON MANAGEMENT OF BOTTOM

SEDIMENTS CONTAINING TOXIC SUBSTANCES

Yokohama, Japan

27 February - 1 March 1990

Co-Chairmen

Mr. Takashi Hashikawa

Director, Environment Division

Ports and Harbours Bureau, Ministry of Transport, Japan

Mr. Jimmy F. Bates

Chief, Policy and Planning Division

Directorate of Civil Works, US Army Corps of Engineers

Tuesday, February 27, 1990

0900-0930 Opening Ceremony

0930-1000 Mr. Mitsugu Kawada, "Summary of Marine Environment Work"

1000-1030 Mr. Jimmy F. Bates, "Overview of Significant Issues and

Trends in the US Dredging Program

1030-1045 Coffee

1045-1115 Mr. Munekazu Hirose, "Mercury-Contaminated Sediment

Disposal Work in Minamata Bay"

1115-1145 Mr. Masaharu Nakamura, "Restoration of Lake Shibayama"

1145-1300 Lunch

1300-1330 Mr. Tatsunori Kosaka, "Construction of Kansai International

Airport"

1330-1400 Mr. Mark J. Otis, "A Pilot Study of Dredging and Disposal

Alternatives for the New Bedford Harbor, Massachusetts,

Superfund Site"

1400-1430 Mr. Zen-ya Yoshino, "Development of the High Rate Dewatering System of Bottom Sediments and Water Blooms"

1430-1500 Mr. Jun-ichi Hamasuna, "Example of Latest Techniques for

Bottom Sludge Dredging"

1500-1515 Coffee

vi
1515-1545 Mr. Michael R. Palermo, "An Update of Dredged Material

Capping Experiences in the United States"

1545-1615 Mr. Takeo Maekawa, "Treatment of Dredged Sludge by

Mechanical Dehydration"

1615-1645 Mr. Kiyoshi Nikaido, "Investigation on Resuspension of

River Sediments Using the Annular Flume During Rainfall"

1645-1715 Mr. Jacob F. Redlinger, "Hopper Dredges Applied to the

Alaska Oil Spill, March 1989"

1715-1745 Mr. Yasuyuki Nakayama, "Oil Cleanup with a Large Skimming

Vessel in Wakasa Bay, February 1990"

1800- Ministry of Transport Reception (Yokohama International

Conference Center Lounge)

Wednesday, February 28, 1990

0900-0930 Mr. Hazime Matsui, "Influence of Anoxic Water in Tokyo Bay

and Its Management Planning"

0930-1000 Mr. Yasushi Hosokawa, "Proposal of the SEA-BLUE Program--

Application of Natural Energies and Biological Activities

to Water Quality Improvement Along Coast"

1000-1030 Coffee

103' 1100 Mr. John F. Tavolaro, "The Problem of Dioxin Contamination

in Sediments of the Port of New York and New Jersey"

1100-1130 Mr. Masashi Kamon, "New Soil Stabilizer from the

Combination of Industrial Waste"

1130-1200 Ms. Catherinc C. Krueger, "Developing Sediment Quality

Standards: Comprehensive Sediment Management in Puget

Sound"

1200-1330 Lunch

1330-1700 Excursion by Yokohama City (Yokohama Port, etc.)

1830- US Reception

Thursday, March 1. 1990

0900-0930 Mr. Nobuaki Wada, "Solidification Technique for Dredged

Bottom Sediments"

0930-1000 Mr. Takeshi Chiba, "Development of a Vacuum Consolidation

Method Employing Horizontal Drains"

vii
1000-1015 Coffee

1015-1045 Mr. Spencer A. Peterson, "Toxicological Assessment of

Hazardous Waste Sites"

1045-1115 Mr. Tsuneyoshi Tanaka, "Follow-up Investigation of Marine

Life Around the Artificial Sandy Beach of Yokohama Marine

Park and Problems Concerning Maintenance and Management

of the Beach"

1115-1145 Closing Remarks

1145-1800 Free

1800- Yokohama City Reception (Hotel Yokohama)

Friday, March 2. 1990

0830-1700 Excursion by Ministry of Transport (Yokohama--Port and Harbour Research Institute--Kamakura--Yokohama)

viii
JOINT COMMUNIQUE

14th MEETING OF US/JAPAN

EXPERTS ON MANAGEMENT OF BOTTOM SEDIMENTS

CONTAINING TOXIC SUBSTANCES

FEBRUARY 27-MARCH 1, 1990

YOKOHAMA, JAPAN

The 14th meeting of Experts on Bottom Sediments Containing Toxic Substances was held from February 27 to March 1, 1990, in Yokohama, Japan,

pursuant to the Agreement between the Government of the United States of

America and the Government of Japan on Cooperation in the Field of Environmental Protection signed in Washington, DC, on August 5, 1975, and renewed in

1980 and 1985. Mr. Jimmy F. Bates, Chief, Policy and Planning Division,

Directorate of Civil Works, US Army Corps of Engineers, and Mr. Takashi

Hashikawa, Director, Environment Division, Ports and Harbours Bureau, Ministry

of Transport, Japan, co-chaired the meeting.

The purpose of the meeting was to continue to implement Article I of the

1975 US-Japan Agreement by conducting mutually beneficial meetings of experts

to explore, discuss, and exchange information on technical and operational

areas, aspects of the management of bottom sediments, and related research

development activities, policies, practices, legislation, and regulations.

Scientific and engineering experts from both countries presented technical papers on a variety of subjects, including operational and pilot demonstration projects and research programs to evaluate and protect the environment. More specifically, the experts discussed evaluating and predicting the

behavior of nutrients, organics, and other contaminants in both in-place and

dredged sediments; pilot projects and demonstrations on innovative dredging

and sediment treatment technologies; follow-on environmental programs to evaluate the success of sediment removal and treatment operations for environmental protection; and identification and evaluation of the many alternatives for

dredging and disposal of contaminated sediments from lakes, rivers, waterways,

estuaries, and marine waters associated with these sediments. New, innovative, and cost-effective technologies including the uses of marine energy and

biology were stressed, and management practices with the most promising longterm utility were emphasized.

This 14th meeting involved a successful and productive exchange of information relating to the dredging technology and sediment management programs

of both countries. To better utilize the knowledge gained and lessons learned

from these exchanges, the Co-Chairmen discussed the possibility of publishing

detailed proceedings which would contain each of the presentations made during

the 14th Meeting and of exchanging a title list of papers on t[* management of

bottom sediments published every year in both countries, and hc.ding the next

(15th) meeting in the United States in November 1991, at a site and time to be

ix 92-10770

92 4 24 203 i11h1 l1
determined later. Such a meeting would be held in accordance with an agenda

to be mutually agreed to in the future.

Jimmy F. Bates Takashi Hashikawa

Chief Director

Policy and Planning Division Environment Division

Directorate of Civil Works Ports and Harbours Bureau

US Army Corps of Engineers Ministry of Transport

March 1, 1990 March 1, 1990

x
OVERVIEW OF SIGNIFICANT ISSUES AND TRENDS

IN THE US DREDGING PROGRAM

Jimmy F. Bates

Chief, Policy and Planning Division

Directorate of Civil Works

US Army Corps of Engineers

Washington, DC AD-P006 451

INTRODUCTION

The purpose of these introductory remarks is to provide the Japanese

Delegation with a brief overview of significant accomplishments that have

occurred in the US Program since the last meeting some two years ago. These

remarks will also represent what is seen as some of the major emerging issues

and US Research directions and information needs in the field of contaminated

bottom sediments management. The objectives of this overview are:

a. To serve as a general introduction to the papers to be presented by

the US Delegation.

b. To provide the basis for information exchange, including any

requested follow-on information that the Japanese Delegation might

desire, on topics of interest which cannot be presented in detail

during our short visit here in Japan.

c. To act as a mechanism to initiate information dialogue with the Japanese Delegation on topics of particular interest to the US Delegation, both during this and follow-on meetings.

SUMMARY OF RECENT ACCOMPLISHMENTS AND EVENTS

Reorganization

In prior meetings, the US co-chairman has been a military officer who

also served as the Director of the Corps Water Resources Support Center and

the Corps Dredging Division, which had the US responsibility for these Memorandum of Understanding (MOU) meetings. There has since been a major reorganization within the Corps, with the broad responsibilities of the Dredging

Division reassigned as a Corps Headquarters management function. As part of

this reorganization, the responsibility for the environmental management

activities associated with dredging and dredged material disposal was assigned

to me as Chief of the Corps' Policy and Planning Division. As such, my boss,

the Assistant Secretary of the Army (Civil Works), felt that it would be more

appropriate for me to assume the duties as US Co-chairman for these MOU

meetings.

The US representation in the future MOU meetings will remain in somewhat

of a dynamic state dictated in part by what the US Congress eventually defines

as the appropriate roles and responsibilities at the Federal level in bottom

sediment cleanup projects within the US waterways. It is clear, however, that

92-10771

932 4 2 4 2 04 {lllllllliilllllIi
both the Corps and the Environmental Protection Agency (EPA) will continue to

play a major role in this area and in future MOU meetings.

Port Deepening

Since the last meeting the United States has made significant progress

in its national construction dredging initiative to deepen our major coastal

deep-draft ports and harbors under cost-sharing requirements of that authorizing legislation. Most affected ports have opted for a phased construction

process wherein channels are to be deepened to 50 ft with a decision on eventual construction to 55-ft depths contingent on future economic conditions and

trends. To date, this effort has involved removal of over 250 million cu yd

of new work dredged sediments. Physical and not chemical contamination

impacts relating to these extremely large volumes of sediments have been the

overriding environmental concern. It is good to be able to report that many

of the innovative beneficial use concepts employed during this construction

and reported at prior meetings have been quite successful, and some excellent

operational experience and data are being developed on these concepts. Two of

the more innovative and promising concepts for future program application are

submerged berms and wetlands rehabilitation projects.

Submerged Mounds

The concept of submerged mounds is to take advantage of the large volumes of clean sediments derived from construction dredging. We use pinpoint

placement in nearshore ocean waters parallel to the beach for the multipurpose

benefits of replenishing the adjacent beach in a cost-effective manner, stormwave and beach erosion attenuation by the berm feature itself, and enhanced

biological habitat through feature construction in the relatively nonproductive nearshore coastal zone. Three demonstration projects presently under

study have applied this concept, and the preliminary data indicate that the

three anticipated benefits can be satisfactorily realized through proper

design and orientation of those dredged sediment features.

Wetlands Rehabilitation

To date, the United States has constructed or rehabilitated over

50,000 acres of coastal wetlands with about 30,000 acres of this total derived

from rehabilitation of Louisiana coastal wetlands with dredged sediments from

port construction activities. Operational experience will continue to be

developed with a variety of dredging plants using thin-lift sediment placement

techniques. Such experience will always be a high-priority need within the

United States due to the critical environmental value of and continuing losses

of wetlands habitat. Also, primary regulatory emphasis will be on rehabilitation as opposed to construction of new wetlands due to concerns over the loss

of other coastal aquatic and upland habitat.

Next, the status of other US initiatives that have been reported during

previous meetings will be summarized.

Multiple Uses of Upland Disposal Sites

The concept is to use confined dredged material disposal sites for other

beneficial purposes such as maricultures while simultaneously using these

2
sites for dredged material disposal. Our primary interest is to define economic incentives to landowners in our efforts to retain existing upland sites

as well as to locate suitable new upland disposal sites. This problem is

particularly acute for many of our coastal navigation projects where land is

extremely scarce and in great demand from many competing interests. A pilot

demonstration project was just completed in Brownsville, Texas, involving

mariculture of commercial shrimp species. The preliminary data and market

analyses indicate that such multiple-use concepts do have considerable potential application in many coastal areas of the United States, both from an

environmental and economic perspective.

Ocean Disposal Testing Guidance Revision

The Corps and EPA have just released for public review proposed revisions to our national environmental testing guidance for dredged sediments

proposed for ocean disposal. This document includes revised and updated guidance on acceptance bioassay test species, procedural requirements for undertaking and interpreting bioassays, quality control procedures, and accepted

analytical procedures for chemical contaminant analyses.

Disposal Management

Strategy Technical Guidance

It is our hope to jointly publish later on this year with EPA a technical guidance document that lays out a framework for evaluating all alternatives (upland, open water, etc.) for disposal of dredged material, from the

cleanest to the dirtiest. The document will include accepted evaluation procedures for testing the effectiveness of engineering controls or management

restrictions such as in-water capping for highly contaminated dredged sediments. Our intent here is to consolidate the international scientific knowledge, including Japanese experiences obtained through these MOU meetings, into

a comprehensive disposal management strategy and to periodically make revisions to keep current with the international scientific literature in this

area. Dr. Mike Palermo of the Waterways Experiment Station (WES) will present

an overview update of recent US experience with capping, which is to be incorporated into this strategy document.

Oil Spill Cleanu,

The events surrounding the catastrophic oil spill in Valdez, Alaska,

last summer have probably been followed in some detail by everyone present.

What may not be known is that several Corps hopper dredges were called into

service to assist in that cleanup. Mr. Jake Redlinger of the North Pacific

Division in Portland, Oregon, will describe our experiences in that effort.

Based on our involvement, there is renewed US interest in appropriately retrofitting several of our Federally owned hopper dredges to better assist in

future oil spill cleanup efforts. Furthermore, the United States is fully

aware of the international technology and capabilities in this area and is

proceeding cautiously in defining the most appropriate future role for Corps

dredges in this type of activity.

3
Shellfish Habitat Creation

A demonstration project that was reported on during the 13th meeting in

Baltimore involved creation of a new oyster habitat within Chesapeake Bay

using dredged sediment. The disposal site was located in a previously highly

productive oyster reef which was decimated because of siltation or other phenomena, either man-induced or natural. The operation consisted of using

dredged sediments to raise the bottom elevation above the bottom turbidity

layer and then to apply a cap of oyster shell for optimum recolonization. The

operation was a complete success operationally, economically, and environmentally. Our efforts now consist of follow-on productivity monitoring of the

new reef as well as in developing a disposal management plan that will allow

use of the area for up to 50 years for disposal and simultaneously provide for

phased and systematic construction of additional reef habitat in a manner that

does not impact previous habitat construction efforts.

EMERGING ISSUES/NEEDS IN THE US PROGRAM

Three specific areas that will to a great extent influence future US

participation and technical information exchange needs in these MOU meetings

will be discussed next. The first, as in past meetings, is the general area

of navigation maintenance and our continuing high-priority efforts to ensure

that extensive dredging and dredged material disposal activities are undertaken in both a cost-effective and environmentally responsible manner. On the

environmental side, one of the major continuing priorities is the development

of predictive tests to measure chronic or sublethal efforts of dredged sediments with particular focus on man-made organic compounds. Mr. John Tavolaro

of the Corps New York District will discuss ongoing US efforts with one of the

most difficult US problem areas at present, i.e., the issue of Dioxincontaminated sediments. Of course, any ongoing or planned Japanese research

in the general area of chronic, sublethal effects will interest us.

On the dredging side, a major new research program, the Dredging

Research Program or DRP, which is oriented in large part to improving both our

dredging plant and dredging operation management efficiencies, has just been

started. Our Delegation hopes to maintain close coordination with the Japanese Delegation throughout the duration of this program. Areas of particular

interest to US researchers in DRP are innovation in automated dredging plant

and subaqueous rock excavation techniques.

The second and rapidly emerging issue in the United States is the

cleanup of highly contaminated bottom sediments. The US Congress is expressing considerable interest in establishing and funding a national program in

this area. As mentioned earlier, the relative roles and responsibilities of

the Corps and EPA in this program, while uncertain at present, are both

expected to be major ones. Ms. Catherine Krueger of EPA Region 10 in Seattle,

Washington, and Mr. Mark Otis of the Corps New England Division will give

papers on two of the major ongoing US cleanup projects to date involving

highly contaminated bottom sediments. The innovative Japanese technology and

operational experience in this area are well known to us through previous MOU

meetings; as US co-chairman, it will be my responsibility to ensure that this

information continues to be made available to US scientists and engineers. As

the development of operational cleanup projects proceeds cautiously in the

United States, one area of particular interest and need from the US side in

4
this area will be any long-term environmental monitoring data that might have

been generated by Japanese scientists and engineers as part of follow-on studies of completed operational cleanup projects in Japan. Other related areas

of particular interest to the US Delegation in this area are Japanese experiences in research on sediment stabilization procedures and technologies and in

volatilization of contaminants at the sediment/air interface in confined disposal sites.

The final area of increased US emphasis and information needs, again

where Japan has developed some very valuable and important operational experience, is in the area of lake restoration. By the year 2000, many of the major

man-made reservoirs in the United States will have surpassed their 50-year

project design life, and some will require major engineering rehabilitation

(possibly involving dredging) to restore intended project purposes such as

flood storage, drinking water supply, and navigation. The US Congress has

recently demonstrated new interest in this area, and Mr. Spencer Peterson of

EPA will present a paper on ongoing US research and development activities, as

well as his views on priority US information needs in this area.

5
MERCURY-CONTAMINATED SEDIMENT DISPOSAL WORK IN MINAMATA BAY

M. Hirose

Kumamoto Port Construction Office, Ministry of Transport

1259-7, Yahata-machi, Kumamoto C., 861-41, Japan

A. Yamaguchi

Environmental Pollution Department, Kumamoto

Prefectural Government

18-1, Suizenji 6-chome, Kumamoto C., 862, Japan

AD-P006 unit11W 1111 4521111II~1111 ~ABSTRACT

IWIUhII 11111 111111 I ro root out Minamata disease, which is representative of pollution-caused diseases, a large-scale

sediment disposal work was conducted with special care

to prevent the secondary pollution due to the work.

The basic approach for disposal work consisted

mainly of two kinds of ideas. One was to install

boundary nets to prevent the mixing of contaminated

fish in the Minamata Bay area and noncontaminated fish

outside the Bay. The other was to dredge mercurycontaminated sediment without disturbance and to confine it in the reclamation area, enclosed by highly

watertight revetment.

This work was commenced in 1977 and is going to

be successfully completed in March of this year with

the disposal of roughly 1.5 million cubic meters of

sediment over a 2 million-square meter area.

INTRODUCTION

This paper outlines the mercury-contaminated sediment disposal work conducted in Minamata Bay as an example of public pollution control work. In

Minamata City, located at the southernmost end of Kumamoto Prefecture in

southwestern Japan (Figure 1), sewage from a chemical factory caused Minamata

disease. Methyl mercury contained in the sewage accumulated in fish and

shellfish in Minamata Bay, causing toxic central-nervous system disease in

those who ate such fishery products in large quantities over a long period of

time. So far, over 2,000 people have been recognized as Minamata disease

patients, of whom roughly 900 have died. The solution to this problem thus

became a most critical task in Japan's environmental administration.

To solve this problem at its roots, it was planned that polluted fish in

the Bay would be made inaccessible to consumers and that mercury sludge deposited over an area of about 2,090,000 m2 in the Bay would be disposed of to

6 92-10772

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Figure . Locaion of Minaa Cty

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restore the Bay's clean environment. The basic approach to sediment disposal

was to construct a highly watertight revetment to reclaim the inner area of

the Bay, to dredge sediment from the remaining contaminated area, and then to

confine it in the reclamation area. When a plan in line with this approach

was finalized by the Kumamoto Prefectural Government, the disposal work was

commenced in 1977. Prior to sediment disposal, boundary nets were installed

to enclose the work area, with an acoustic fishway controller installed at the

navigation opening to prevent the mixing of contaminated and noncontaminated

fish. During the whole period of work, special care was taken to complete the

work as quickly as possible and to prevent a new public nuisance due to work

implementation.

Work was implemented, on commission by the Kumamoto Prefectural Government, the Ministry of Transport, which had extensive experience in sludgerelated work, particularly in Japanese ports and harbours. As a result of the

active effort by a number of people taking part in the work, sediment dredging

was finished in December 1987. Then, on February 26, 1988, the Kumamoto Prefecture Minamata Bay Public Pollution Control Work Supervisory Committee confirmed, on the basis of sediment sampling and analysis result, that all

sediment with mercury concentrations exceeding the criterion had been removed.

This result showed the successful completion of mercury-contaminated sediment

disposal work in Minamata Bay.

PLANNING

Mercury Sediment and Minamata Disease

Minamata Bay is a small bay in Yatsushiro Inland Sea. This Bay, whose

mouth is protected by Koijishima Island, forms a naturally excellent port,

which has been developed as a key access to the Minamata-Ashikita industrial

area, home to many chemical factories, and as the base for sightseeing boats

linking nearby tourist islands called Amakusa and the mainland called Kyusyu.

However, over a long period of time, from 1932 to 1968, mercurycontaining sewage had been drained from Chisso Corporation's Minamata factory

into the Bay, causing the development around 1953 of what is now called

Minamata disease. The disease was first officially recognized as a pollutionrelated disease in September 1968. This toxic central-nervous system disease

was caused by long-term ingestion of the Bay's fishery products with high

mercury concentrations.

Planning for Mercury Sediment Disposal

Developments Toward Implementation

In March 1974, the Director-General of the Environmental Agency, the

Minister for Transport, and the Governor of Kumamoto Prefecture reached a

basic agreement on the implementation of Minamata Bay public pollution control

work. This agreement specified that the Kumamoto Prefectural Government, the

manager of the Port, be responsible for the work, while the Ministry of Transport be commissioned to implement the major part of the work, primarily

because of its scale and rich experience in this kind of work. Subsequently,

governmental agencies and expert6 were concerned wiLh detailed studies, which

the Kumamoto Prefectural Government used in June 1975 to develop the Minamata

8
Bay Sludge Deposit Disposal Plan and the Basic Plan for Supervision of

Minamata Bay Sludge Deposit Disposal. In accordance with the Disposal Plan,

the Kumamoto Prefectural Government commenced in October 1977, prior to the

major work, installing boundary nets to block fish movement into and out of

the work area.

In December 1977, however, some local residents, who were concerned as

to the occurrence of a secondary public nuisance due to the work, applied to

the Kumamoto District Court for a provisional injunction against sludge dredging in Minamata Bay. In response, the national government and the Prefecture

temporarily suspended work to avoid local confusion and strove in court to

achieve the residents' understanding of work safety. Consequently, the application was dismissed in April 1980, and the work was resumed in June.

Basic Plan for Mercury Sediment Disposal

Disposal of sediment with 25 ppm or higher total mercury concentration

was planned--a criterion calculated on the basis of the Provisional Standards

for Removal of Mercury-Containing Sludge, established in August 1973 by the

Environment Agency, and finalized through the deliberation of the Kumamoto

Prefectural Antipollution Measure Council. !ccordingly, it was necessary to

dispose of roughly 1,510,000 m3 of sludge from an area of about 2,090,000 m2

in Minamata Bay. Contamination was serious in terms of both mercury concentration and sediment thickness in the Bay's inner area, into which sewage

flowed from Chisso's Minamata factory. Contamination gradually lessened toward the outside of the Bay (Figure 2).

in ppm

Figure 2. Mercury concentration distribution (before

planning)

9
It was planned that the most severely polluted inner area, 580,000 m2 in

size, would be enclosed with a highly watertight revetment, reclaimed with

sludge dredged from the remaining work area, and ultimately covered with goodquality mountain soil.

Existing port facilities in Minamata Bay, all in the newly planned

reclamation area, were to be totally phased out of service as the work progressed. To replace them, Zone I (for constructing the so-called Midori wharf

in advance through preceding work) was planned outside the main reclamation

area called Zone 2, shown in Figure 3. In Zone 2, all stages of work, from

revetment construction to dredging and reclamation, were to be conducted but

on a small scale; therefore, this zone was also regarded as a pilot zone for

checking the safety of the work method to be adopted.

To prevent polluted fish from mixing with nonpolluted fish, double fish

netting was to be installed to enclose the work area during work and for an

appropriate length of time thereafter if necessary, except at the navigation

route where an acoustic fishway controller was used to keep the fish off.

After the completion of sludge disposal, fish in the work area and boundary

nets will be removed.

Figure 3 shows the sediment disposal plan along with the water quality

monitoring points that are mentioned later.

Prevention of New Public Nuisance

The measures taken to prevent a new public nuisance due to work implementation are as follows:

a. First, to stabilize water in the dredging area and in front of the

reclamation area, a cofferdam was temporarily constructed between

Koijishima Island and Myojinzaki's end prior to work. This cofferdam

stagnated the intrabay current, thus accelerating the suspendedsludge settlement and preventing this sludge from spreading out of

the Bay.

b. Second, until reclamation sludge was completely confined with mountain soil, the reclamation area was kept under water to prevent

direct sludge exposure to sunlight and air. As it was pointed out,

this exposure might methylate inorganic mercury in sludge.

c. Third, to anticipate and avoid a secondary public nuisance, the

Kumamoto Prefectural Government established a system for monitoring

the influence of mercury-sludge dredging on water quality, fishery

products, and plankton.

Besides, prompt feedback of monitoring results of water quality to work

was ensured. It was also decided that these monitoring results should be

promptly announced officially to residents and referred to the supervisory

committee, organized by experts, resident representatives, etc. If such results were found to deviate from the supervisory standards, work should be

suspended, or other relevant measures taken.

10
General water area Legend

-' Dredging area

____ lig-'n area

. - 0 Basic monitoring point

'~' - . V Subsidiary mcnitoring point Moved with dredging mite

0 Underground-Water nonitorixig

,j point

4 p clan - Boundary net

Vt C- Capture net

v~ --- Partitlon net -.. Bottom set nat

SoA Sonic fish repelling device

CMSea faming facility

5Dreding area I Filling-in revecment,

Tota 2.92,00 (1 ha)10,0 

Zone I Se leci o

esignor Requiement

Rukuto Bay whaf) m urysted

tablq 

Arta

t l l / -i n 5 a 2 , 0 0 0 - 2 7 2 6 , 0 0 m 3. - ,

area

{Zone /,0 Zone 2 538,000"

Dredging 1.510.000 784,000

ores 1) 0.5 1 "kx

To~al 2,92, m11,510,000 ii

Figure 3. Sludge disposal plan and water quality monitoring points

REVETMENT

itructural Tye Selection

lesign Requirements

Reclamation revetment for mercury sediment confinement had not only to

tithstand earth pressure of reclaimed sludge, wave force, and earthquake

otion, but also to be sufficiently watertight to prevent mercury exudation.

iince earthquakes are particularly frequent in Japan, maintenance of watertightness even during earthquakes was of vital importance. Another requireent was to securely and promptly secure the revetment to overcome the problem

aused by existence of thick silt deposits on the seabed. In consideration of

hese requirements, the steel sheet pile cellular cofferdam type revetment was

dopted.

11
Steel Sheet Pile Cellular

Cofferdam Type Revetment

A steel sheet pile cellular structure is usually made of steel sheet

piles assembled into a cylindrical shape cell, which is filled with sand or

gravel. Since the earth pressure of the fill in the cell is supported by cell

tensile force, such a structure of unified cell and fill is self-sustained and

excellent in water shielding.

The simplest form of this type of structure is detached circular cells,

which are often used as dolphins and detached piers. This structure can also

be used to construct continuous walls in various ways, of which the continuous

circular cell technique was chosen for the present work. The detached cell

type, already in wide use in Japan, is high in work safety because each cell

was sell-sustained in design, but the continuous wall type was more stable

because of the restriction of each cell's movement. In the continuous type,

circular cells are constructed separately and then linked together.

In the present work, cells roughly 30 m in diameter were used with sand

filling, as a result of design consideration. Figure 4 shows a view of the

steel sheet pile cellular structure and its installation, and an example of

its design section at the mooring part with the soil improvement.

Construction Revetment

Soil Improvement

The upper layer of seabed in Minamata Bay (about 10 to 20 m thick) consists of soft silt deposits with a soil strength of almost zero N-value.

Thus, soil improvement was required to maintain the structural safety of the

revetment. Selection of soil improvement methods depends on how each part of

the reclamation revetment will be used in the future after the disposal work.

Considering also other factors involved in this project, basically, the sand

compaction pile method was adopted for the mooring portion and the sand drain

method for the remainder.

Prior to soil improvement work, the sediment was covered with sand,

using an exclusive sand-scattering working ship with a special function, to

prevent work disturbance of bottom sediment, insofar as possible.

Steel Sheet Pile Cellular Cofferdam

To construct the cellular cofferdam with high precision in a short time,

the prefabrication method of construction was used in this work. In this

method, sheet piles were assembled in advance into cylindrical form and driven

into a fixed place of the reclamation revetment to be planned, simultaneously.

The procedures for installing a cell were as follows:

a. Sheet piles assembly into a circular-cell-shaped guide frame at the

assembly base in water of Minamata Bay.

b. Guide frame erection with assembled sheet piles in place to be

driven.

12
steel shieet Pile Cellular Structure

Diamneter of 29.5 m

(232 jgin nl)

F47/L~ ~ ~~~~~. ___________ 4-.36 

.,:SAND.F1 LL:-3,me

Gra~vel 11ound

Figure 4. Installation and the standard design section of steel sheet

pile cellular structure

13
c. Simultaneous driving of all 232 sheet piles with 48 vibrohammers for

each cell.

d. Removal of guide frame and filling of a cell with sand.

After all cells were installed, they were linked to each other with the

sheet pile, assembled into an arc-shaped plate to make a continuous wall.

MERCURY SEDIMENT DREDGING

Basic Concept

Dredging Planning

The important points kept in mind in sediment dredging were minimization

of the work period to eliminate resident anxiety as early as possible, and the

control of muddiness to prevent a new public nuisance. On the other hand, it

should be noted that:

a. Most of the mercury contained in the sediment in Minamata Bay is

inorganic, which does not easily desorb from the soil particles into

the water.

b. Methylation of inorganic mercury in dredging poses no problem if

aerobic conditions can be avoided.

Special care was also paid to minimize extra dredging so as to permit

the accommodation of all dredged sediment in the reclamation area as planned

ana to achieve the completion as early as possible. Mercury was contained

basically only in the upper thin layer of bottom sludge in the Bay. Whereas

the reclamation area, planned L the inner part of the Bay, had a fairly thick

layer of contaminated sediment .s compared to other parts, the dredging area

required only an average of roughly 50-cm-deep dredging. However, the thickness of the layer to be removed by dredging was accurately and carefully identified to ensure the elimination of all polluted sediment, as well as to minimize extra dredging so as to save time and cost.

Adoption of Cutterless Suction Dredger

Since bottom sludge disturbance due to dredging could cause mercury elution, a dredging method was carefully chosen so as to minimize muddiness. A

conventional suction dredger cuts into the sea bottom at the suction mouth and

then pumps up sediment to be removed. The sediment disturbance by the cutter

causes muddiness. To reduce the muddiness substantially, a suction dredger

without a cutter was developed specially for sediment dredging in Minamata

Bay. Since the rl,,'terless suction dredger had already been used with great

success in sludge dredging, but on a smaller scale, in Tokuyama Bay and

Yokkaichi Port of Japan, the use of this type of suction dredger was decided

upon with a slight modification for the present work.

Implementation and Execution Control

Sediment was dredged with four cutterless suction dredgers because only

four of all existing cutterless suction dredgers were found to be applicable

14
to the present work with a slight modification. They differed from each other

in their dimensions. The work area was divided into four portions for convenience. Then each of the above-mentioned four dredgers was assigned to a

portion according to its properties.

All suction heads of these dredgers, including the mouth, were modified

in advance as shown in Figures 5 and 6. Major modifications were as follows:

a. The suction mouth shape was modified to suit Minamata Bay's sludge

properties through the experiment with similar soft mud.

b. Provisions were made for monitoring muddiness near the suction mouth.

For this purpose, two kinds of systems were adopted: continuous

measurement of turbidity and direct monitoring with an underwater TV

camera. For turbidity measurement, continuous-type turbidimeters

were attached to the suction head, with readings displayed in the

dredger overation room. For visual check of muddiness, an underwater

TV camera was mounted on the suction head, together with sight var es

positioned at constant intervals. Muddiness was checked on the TV

monitor in the operation room on the basis of the view of the vanes.

Besides, it was confirmed in advance through the model experiment

that the vane visibility distance was correlated with turbidity.

These two systems enabled the dredger operation in the operation room

to check muddiness around the suction head and thereby take the

necessary measures such as slowing down dredging speed.

Procedures to minimize extra dredging were as follows:

a. Prior to dredging, submarine topography and sediment thickness were

accurately measured for the dredging area.

b. Submarine topography afLer ideal sediment removal without any extra

dredging was expressed with contour lines.

c. Since equal-thickness dredging was not technically feasible, a certain area was to be dredged to a uniform level; therefore, the dredging area was divided, in 30-cm units of thickness to be removed on

the basis of the above-mentioned contour lines, into segments in

which dredging to a uniform water depth would eliminate at least all

subject sludge.

d. To ensure high precision, enhance efficiency, and monitor dredging

conditions, dredgers were furnished with various sensors, whose data

were processed via microcomputer and displayed on the monitor screen

in the operation room.

The major data obtained through the above operation management system,

based on the measurements of various sensors loaded on each dredger, as well

as the basic principle to obtain these data, were as follows:

a. Dredging thickness. The suction mouth was on the side of the suction

head, which swung left and right while pumpiag sediment. Therefore,

echo sounders were installed on both left and right sides of the head

to determine the dredging thickness from the difference between the

15
Left echo sounder

Lfrt echo enuner

Figure ~ ~ ~ uto ~ rde 5.Ctels ~~~sr esrlctoseno

Densiq Rear eho utter sonder rnt echo one

0 terde

Figureutio 6.Sutinaea

Figre5.Cuteles uciondrdgr enorlo16on
readings of the two sounders. Since the inclined head gave the distorted measurement, a clinometer was also attached to the head to

correct the resulting thickness data.

b. Submarine topography before and after dredging, The dredger moved

forward while swinging its suction head and dredging. Therefore,

sounders identical to the above-mentioned ones were also installed on

both front and rear sides of the head to survey submarine topography

before and after dredging. Errors due to the head inclination were

corrected in the same manner as described in dredging thickness.

c. Suction head position, swing speed, and swing direction. In addition

to electric positioning equipment, the suction head was provided with

a gyrocompass to measure the head position, swing speed, and swing

direction.

d. Dredged volume and mud concentration. To measure these data, a current meter and a density meter were installed in the dredger discharged pipe. Both meters were used to manage the effluent treatment

system.

Resulting measurements, together with other necessary data for execution

control, were processed via microcomputer onboard and displayed in real time

on the monitor screen in the operation room. Figures 7 and 8 show an example

display and the summary of dredging work, respectively.

The discharge pipe was also improved to prevent sludge exposure to air

and sunlight, both of which promote methylation of inorganic mercury in

sludge. In addition to this improvement, the discharge outlet in the reclamation area was submerged in water, with the discharged sludge kept underwater

during work.

Effluent Treatment

Effluent Treatment Planning

The ordinance issued by the Prime Minister's Office stipulates that

effluent from the land reclaimed with harmful earth/sand must not contain

mercury exceeding 0.005 ppm. Since a mercury analysis takes a lot of time,

turbidity, which is correlated with mercury concentration and can be measured

in real time, was also monitored as the quickest information for efficient

operation of the effluent system.

The following points were kept in mind in designing effluent treatment:

a. To increase natural sedimentation in the reclamation area, the effluent flow distance was maximized by commencing reclamation from the

innermost portion and by providing partition cofferdams in the area.

b. Precipitation in the reclamation area was estimated on the basis of

past data, and then the result was incorporated into the effluent

treatment plan.

17
SY SID21,

(M) 1986/05/19 14:31t25 Zone (D22] Swing No. [26] (W)

PlAnnQd Original (In dredging)

8 proilo a eabed Dredged .8

-result uction hend position

lu 10

-40 -20 -10 0 ( 1 0) 20 30 40

(Dr~adging-result)

Figure 7. Example display on monitor screen

Dredging Discharge

Sludge dredger Filling-in

Discharge pipe

Figure 8. Dredging work

18
c. Before discharge, effluent was to pass through the effluent treatment

facility, which was composed primarily of a mixing tank, flocculant

mixer, flocculation tank, settling tank, and rapid filter.

d. Since effluent treatment, unlike dredging, can be controlled even at

night, 24-hr treatment was designed.

Treatment Procedure

Sludge discharged into the reclamation area had to be kept underwater at

all times to prevent direct exposure to air and sunlight. Water depth was

checked every morning to ensure at least 50 cm as a general rule.

Since rainwater inflow from the existing land into the reclamation area

lowers the effluent treatment efficiency, a side ditch was installed between

the land and the reclamation area to divert rainwater flow from the land.

With these points kept in mind, effluent was treated in the following

manner:

a. After natural sedimentation in the reclamation area, supernatant

water was first subjected to water quality testing to determine the

need for flocculant addition and, if needed, the appropriate amount.

b. Water was first sent to the mixing tank, where a flocculant was added

if necessary, then to the flocculation tank, and finally to the settling tank, where flocs settled.

c. Resultant effluent flowed into the monitoring tank for water quality

testing.

d. If the discharge criterion was exceeded, effluent was sent back to

the rapid filter for thorough purification.

It was planned that if muddiness exceeded the supervisory standard, effluent discharge would be suspended. However, so far muddiness remained well

below the standard, so no hindrance occurred to the operation.

SLUDGE CONFINEMENT

Sludge discharged into the reclamation area required covering with mountain soil and other good-quality earth/sand for confinement. Since sludge was

high in the proportion of fine particles, extremely high in water content, and

low in bearing capacity, earth-covering work would be inefficient and almost

impossible if conducted over such sludge as it was. To increase bearing

capacity sufficiently for subsequent earth-covering work, the sludge surface

was subjected to the following two processes:

a. The entire reclamation area was covered with a sandproof membrane to

disperse the concentrated load to be imposed.

b. Sirasu (volcanic ash earth/soil of low specific gravity, locally

produced), which generates strength with light weight, was sprinkled

19
over the sludge to the thickness of 80 cm because of the bearing

capacity consideration.

These processes, always carried out underwater (50 cm or more deep) to

prevent sludge exposure to air, imparted the required bearing capacity to the

sludge surface, making smooth and efficient earth-covering work possible.

After water in the reclamation area was drained, good-quality mountain soil

was sprinkled over the sludge and leveled for complete confinement.

SUPERVISION

Monitoring Plan and Results

A thoroughgoing monitoring plan was developed to prevent a secondary

public nuisance due to sediment disturbance and dispersion with work, or to

exudation of harmful substances from the reclamation area. In response to

resident anxiety as to work safety, continuous monitoring was planned for

water quality and fishery product contamination.

In the water quality studies (Table 1), basic monitoring points were

provided along the work area boundary to prevent work influence beyond that

area. Subsidiary monitoring points were also provided between the basic monitoring points and the current working points to predict water quality at the

basic monitoring points for expeditious assessment of work propriety. On the

other hand, in the fishery product contamination studies (Table 2), periodic

sampling and analysis were conducted, together with fish culture experiments

in Minamata Bay and plankton investigation, to ensure that work implementation

would not pollute the aquatic life in the Bay. The locations of the water

quality monitoring points and the sea-farming facility for fishery product

monitoring are shown in Figure 3.

These monitoring practices were carried out under the direction of the

Kumamoto Prefectural Government. To confirm work safety from an objective

standpoint, the Minamata Bay Public Pollution Control Work Supervisory Committee was established in December 1976 as an advisory organization to the Prefectural Government. The Committee consists of eight experts, four staff

members of administrative agencies concerned, three members of the Prefectural

Assembly, and ten resident representatives. Committee meetings are open to

the public as a general rule.

Water quality testing in accordance with the monitoring plan revealed

that turbidity, hydrogen ion exponent, chemical oxygen demand, and dissolved

oxygen showed variations probably attributable to natural environmental

changes (rainfall, red tide, etc.) but that mercury concentration and all

other items remained below determination limits or did not exceed supervisory

standards. Work safety was thus confirmed.

None of the fish sampled outside the work area exceeded the supervisory

standard for total mercury concentration. Continuous investigation into total

mercury concentration changes in fishery products in the work area revealed no

noteworthy changes suggestive of work influence.

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CN~1. -10 r W- 0 1.4 g 0 ( 0d 0 Q(0 -4 01-4 0 ) $

co C.dU

U) E 4-))

"-4 V

4)4). -)

00

" . 4J

0t~2 0

U) CU1 U

'4 - -4 -,

0. 4"

23
Confirmation of

Sediment Dredging Completion

It was determined in advance that sludge dredging would be adjudged completed if the average mercury concentration of four grid points of a mesh was

below 25 ppm in each of the meshes (200 m-interval meshes as a general rule)

established to determine the dredging area and the investigation points of

mercury concentration.

In December 1987, just after completion of dredging work, the Kumamoto

Prefectural Government sampled and analyzed sediment in the dredging area and

its peripheral area to determine mercury concentrations in individual meshes

(Figure 9). According to Figure 9, the highest concentration was found to be

8.75 ppm, far below the criterion of 25 ppm. In addition, the comparison

between the results in Figure 2 and Figure 9 shows the great improvement of

the Bay environment after the dredging work. This finding was reported on

February 26, 1988, to the 60th Supervisory Committee meeting, where completion

of Minamata Bay mercury sludge dredging was formally confirmed.

CONCLUSION

Sediment dredging work, which was the main part of the whole disposal

work planned, had been successfully completed in December 1987. The completion without the occurrence of any new public nuisance relieved the residents

of much anxiety. Since 1977, disposal work in Minamata Bay has been carefully

carried out with environmental control. Tnis is natural in recognition of a

great fear of dealing with the special matter of mercury-contaminated sediment. Thus, it was necessary to develop and improve the working method and

equipment because of the special mercury properties.

Disposal work is now smoothly approaching completion this March with the

final act of earth-covering work, after about a 10-year struggle against

Minamata disease.

In this port, the so-called "Marine Town Project," a series of waterfront development activities was planned and actively started for local

revitalization. It is hoped that by taking advantage of the coming completion

of the disposal work, this revitalization would be well advanced with the

effective utilization of the sludge-reclaimed land.

24
0 05

Figure 9. Mercury concentration distribution after dredging work

25

2 .4 24 20 6
AD-P006 453

11 IDRESTORATION mil IIA OF LAKE A

M. Nakamura

Japan Sediments Management Association

2-7-12, Tsukiji, Chuo-ku, Tokyo 104, Japan

ABSTRACT

The pollution of lakes in Japan is serious in

all parts of the country. Although Lake Shibayama is

a small one, or a swamp, its pollution is not treated

lightly, because many people visit the hot spring spa

on its shore. Pollution studies started in 1981; the

work on the restoration project was actually begun in

1986. As a restoration technique, the dredging of

sediment was employed. This paper describes the pollution studies and the management of dredged material

activities.

TOPOGRAPHICAL BACKGROUND

Lake Shibayama is situated in the northeastern part of Kaga City, 40 km

(southeastern direction) from the capital city of Prefecture Ishikawa,

Kanazawa (Figure 1). It is one of the three Kaga lakes including Lake Kiba

and Lake Imae (Figure 2).

It is an inland-sea lake born inside a sand dune. The national reclamation work aiming to spread farmland in this area started in 1952 and changed

the topographical forms of the three lakes. Lake Kiba was isolated, Lake Imae

disappeared, and Lake Shibayama lost two-thirds of the whole lake area by

landfill. As a result, the lake water which flowed previously from Kakehashi

River to the Nippon Sea via Kushi River had a new flow line connecting directly to the Nippon Sea.

Lake Shibayama has a surface area of 192 ha and a mean depth of 2 m.

Since the lake has become important in river conservation, it is now

administrated as a secondly graded river.

Lake Shibayama is located in the Kaga hot spring resort and has a spa on

its shore. It is regarded as an important lake for sightseeing, agricultural

water usage, inland fishery, and wildlife habitat. The area between the lake

and the Nippon Sea was the ancient famous battlefield (Shinohara's) in the

Genji and Heike Wars. Around the site remain many sad stories such as the

"Head washing pond," where Sanemori Saito, General of Heike, washed his neck.

26 92-10773 $2 4 24 2 0 7 lliilitll!Elil~i 1g
Tny..* nl,,

Pref.Islkawa

Lake Shlbay a e rf.T0Y

,Pe r reI.G/ Iu

F0 e f" . F.uku I

Figure 1. Location of Lake Shibayama

N akehasi River

Lik( hlbyliiLake ,11b.

Figure 2. Location of the three Kaga lakes

ENVIRONMENTAL BACKGROUND

The water pollution of the lake began to increase in 1965 as a result of

urbanization of its surroundings and accelerated the erection of sewage facilities, which resulted in no further marked pollution for a while. However,

the eutrophication increased owing to the release of nutrients from sediment

that had accumulated on the lake bottom. This process is a fatal phenomenon

of a closed water area.

The Prefectural Government started to implement the lake restoration

project in 1986, which consistea of the removal of sediment and the reduction

of internal loading.

The water area near the lake was acknowledged as an A-rank category in

1974. As previously mentioned, the rank is due to the highly needed

27
protection of lake environments and to the significant evaluation of the

important sightseeing resources of the Katayama spa. But because of the difficulty of attaining the desired standard within a short time, the lake is now

recognized as a B-rank category for the time being.

The downstream area of the Iburibas'ii River and the whole area of the

Yokkaichi River were acknowledged as a B-class category. The environmental

standard of the lake is applied to the Shinbori River, newly excavated for an

outflowing line, because of the short length and the antitide floodgate

erected at its estuary.

POLLUTION STUDIES

The environmental protection division of the Prefectural authorities

started to carry out pollution studies related to the eutrophicated conditions

of Lake Shibayama in 1981. The river engineering division entrusted our sediment management association with various investigations, including water and

sediment surveys, analysis of them, and planning of sediment removal work.

From measurements of ignition loss, chemical oxygen demand (COD), total

nitrogen, and total phosphorus, which are of special concern in lake pollution, maps of their plane distributions were made, as shown in Figures 3

and 4.

I , -

----------

V"_. I ' ! X" T N/

- ------------- ~s

rigure 3. Plane distribution of Figure 4. Plane distribution of

T-N T-P

Vertical profiles of T-N and T-P in sediment were also made, as shown in

Figures 5 and 6.

From these plane and verti distributions of pollutant, the removal

area and the sediment depth to b-L removed were decided so that the former is

85 ha, corresponding to 44 percent of the whole lake area, and the latter is

0.5 m. The quantities to be removed are 42,500 m 3 .

Table I indicates the fundamental sediment properties. The sediment

samples were taken from three kinds of sediment depth, that is, 0 to 10 cm,

20 to 30 cm, and 4U to 50 cm. The ratio C/N, which represents an organic

pollution degree, was 11.3 (upper layers), 10.4 (middle layers), and 10.5

(deep layers).

28
T-P T- -N

1 2 3 4 mg/g 1 3 4mg/g

4j

20. 0) 20

Q))

/ o / m40 u 40-

Q) :) (a

cmm

Figure 5. Vertical profile of T-N Figure 6. Vertical profile of T-P

OUTLINE OF WORK

Figure 7 shows the total dredging areas and disposal site areas. Figure 8 illustrates the yearly completed sections, as summarized in Table 2.

Considering the noisy effects to the spa, the dredge with an electric

pump motor was adopted in 1986 and 1987 and the one with a diesel engine in

1988. The noise level at an inn nearest to the noise source was about 55 db,

because a special silencer was attached to the diesel engine. Therefore, no

complaints were voiced from people at the spa. The dredged material was conveyed directly to the disposal sites, and the spill water was discharged after

sedimentation with Ilocculants. Figure 9 shows a flowchart of the work.

Disposal Sites

As shown in Figure 7, the dredged material was disposed in the agricultural paddy fields northwest of the lake. The disposal area in 1986 was

200,000 m2 located in farmland on the right bank of Shinbori River at the

Ikiri division of Kaya City. The embankments had a total length of 6,670 m,

and foot paths between the rice fields of 5,840 m. A section of embankment is

shown as Figure 10.

The disposal area in 1987 was 190,000 m2 located in farmland on the left

bank of Shinbori River at the Shinohara, Shinohara-Shin, and Ikiri divisions

of Kaya City. The planned disposal area in 1988 was 100,000 m2 in farmland

along Hokuriku Highways on the right bank of the Shinbori River at Ikiri Town.

Disposed Thickness

Considering the working efficiencies of cultivators after sun drying,

the disposed thickness was 15 cm in 1986, 30 cm in 1987, and 30 cm in 1988.

29
TABLE 1. SEDIMENT PROPERTIES

Sediment Depth (cm)

Upper Middle Lower

Parameter 0 - 10 20 - 30 40 - 50

Water content, % range 93.4 - 177 130 - 200 78.3 - 188

average 151 164 138

Specific gravity range 24.81 - 26.08 2.525 - 2.624

average 2.562 2.577

Unit vol. weight range 1.19 - 1.35 1.19 - 1.32

(grain size), g/m 3 average 1.18 1.27

Coarse range 0 - 0.10 0.0

sand average 0.04 0.0

Fine range 0 - 8.0 0 - 5.8

sand average 2.5 1.7

Silt range 66.2 - 82.8 30.4 - 87.7

average 73.6 52.4

Clay range 13.7 - 33.8 12.3 - 62.7

average 23.9 45.9

Ignition loss range 11.6 - 14.6 11.2 - 14.8 87.7 - 12.4

average 13.3 12.4 11.4

COD, mg/g range 44.1 - 60.2 43.1 - 69.0 25.4 - 52.1

average 51.3 50.2 43.4

Sulphide, mg/g range 0.04 - 1.30 0.09 - 4.10 0.04 - 5.30

average 0.29 0.72 0.46

T-N, mg/g range 2,330 - 4,030 2,280 - 4,350 1,820 - 3,420

average 3,293 3,151 2,821

T-P, mg/g range 1,370 - 2,510 802 - 2,708 604 - 1,780

average 1,908 1,317 965

T-C, mg/g range 33,600 - 47,100 25,700 - 38,300 19,900 - 35,400

average 37,294 32,731 29,613

30
Nippon Sea ~- '

. ..... ...

.P~~, - 0 

Figre7. otl dedin an dspoalsit aea

198..

Nippon Sea ' " '

40

,0.'

00O"~

4 

,

Figure 8. Yearly completed sections Of Lhe dredging and

disposal areas

31
TABLE 2. YEARLY COMPLETED WORKS

Entire

Parameter 1986 1987 1988 Total Plan

Dredging area, m2 61,600 96,000 60,000 217,600 850,000

Removal depth, m 0.5 0.5 0.5 0.5 0.5

Removal quantity, m 3 30,800 48,000 30,000 108,800 425,000

Finished percentage 7.2 11.3 7.0 25.5 100

Dredging

Considering removal accuracies and generated turbidities, the dredge

with a cutterless pump (E350 ps, D600 ps) was adopted for thin-layer (0.5 m)

dredging. Especially for the purpose of removing efficiently a suspended

layer just overlying sediment, the dredging was conducted as a two-time cutting method. The effective swing width was 25 m, and the practical width

including lap allowance was 30 cm.

Hydraulic Conveying

The distance from the dredge to the disposal sites was 2,070 m in 1986;

between 2,200 and 3,200 m in 1987; and an average of 2,800 m in 1988. As

these distances exceed the practical limit of a 350-ps dredge, an intermediate

pump of E350 ps was installed. The piping system was arranged so that floaters were set on the seaside, and the pipe supports with two heights (h - 0 and

h - 1 m) were equipped on land. The following tabulation shows the various

boats used in this work.

Boats No. Capacities

Dredge I E350 ps

Cutterless 1 D600 ps

Booster pump boat 1 E350 ps

Anchor pulling-up boat 1 60 ps, 3 t lifting

Traffic boat 1 3 t, D10 ps

32
Setting of Assembling of Provisional Water clarifyiril

conveying pipes dredge embankment facilities

[Dredging

I Conveying

Booster puwp 1

station

Injection of Conveying

flocculants

SDisposing to

rice fields

I Spill d..rater

'ater treatment I

Clarified water

Discharging j

Di smantlin k updrdeeovn of Dismantling of

of pipes E enb a nkment water plants

Figure 9. Project operations activities

33
Figure 10. Section of embankment

Treatment of Spill Water

Spill-Water Quality

The effluent qualities standards in Table 3 are applied to the basin

adjacent to the lake and the Shinbori River according to the regulations of

Prefecture Ishikawa. The spill-water quality was decided as follows based on

the effluents standards:

SS: 70 mg/i on an average

100 mg/1 at maximum

pH: 5.8 - 8.6

TABLE 3. EFFLUENT STANDARDS APPLIED TO THE SHIBAYAMA BASIN

Shinbori River Area Permissible Limits

Factories and BOD COD SS

Businesses (1974) Ave. Max. Ave. Max. Ave, Max.

Stock raising, 80 120 80 120 100 150

foodstuff industry,

hospital, refuse 30 40 30 40 70 90

burning, urine

facilities

Sewage end 20 30 20 30 70 90

facilities

Others 60 80 60 80 80 120

Places having

sewerage 20 30 20 30 70 90

Places having sewer- 120 160 120 160 120 180

age projects

34
Treatment

For the treatment of spill water, an agglomeration system was adopted

considering the short and temporary nature of the work and the spill-water

quality previously discussed. Figure 11 shows a flowchart for this system.

The size of the settling pond was decided considering the retention time of

irnflicnts, water ,,rface loading, etc.

edimentatin7 Treated

Raw water with d Settling pond water flocculants

Flocculants adding

Polymer inorganics

Dredging Conveying Conveying _31tion pipes-[ Settling D cag

ngn' pipes at farm- pond D ]

Figure 11. Agglomeration system for water treatment

Installations for Water Treatment

Clarification of spill water consisted of two methods: an injection of

polymeric flocculants into the conveying line, and a showering of inorganic

sulfuric aluminum (sometimes mixed with polymer) at the settling pond. The

quantities of medicines used are indicated in Table 4.

TABLE 4. ANNEXED MEDICINES

Method Flocculants Quantities Added

Pipe injection Polymeric flocculants 40 g/sediment m3

Inorganic flocculants 80 g/dredged material m3

Showering Sulfuric aluminum

Polymeric flocculant 1.5 g/dredged material m3

35
The monitoring of discharged water pH and turbidities was conducted two

times per day to control the running conditions by comparing to the annexed

quantities.

Automatic feeder stirrer 2.2kW

Max. 80 mm/Hx. 0.75 kW Pol mer njnctn) pume

,opp 200 L F 12. F owchartinjection 30 m/0x5 pipe 80A VP pi 

ResultrofqTratmen ntoeeritt ppet

eSedrimt i slutien Ttfy

pup 80A x 3.7 kw/"j _

ano-ei re im w h th io dr edge a re e rein

1986. A signifaent i

drege aresul oupiedolyi.2tecntof the wholle.wtrseemstynatralitha

the restoation e ts shl ape tete dreging ofboupleti25 per

ofe sare. thnrore i. i oghtt f tey wil apent

it occupesuoly55ret aprpithe of eontirste Envionmea qioety Projsfect

ofe laesuato sandavrs.. Theere irtt ias neytrcninuoetiork. ithea

agrcultral us cofo h drededgmateriltbrougtabtl a3-ereticraei

RESULTS OF RESTORATION

To see the effects of dredging it is important to observe a summer

peak, which is a phenomenon generated by highly released quantities of nutrients from the sediment in summer. The concentrations of chlorophyll-a, T-P,

and T-N in sediment were compared with the dredged and undredged areas in

1986. A significant improvement was not recognized at the time when the

dredged areas occupied only 7.2 percent of the whole. It seems natural that

the restoration effects should appear after the dredging of about 25 percent

of the area. Therefore, it is thought that they will appear in the future.

SUMMARY

This work was carried out for three years from 1986 to 1988. However,

it occupies only 25.5 percent of the entire Environmental Improvement Project

of lakes and rivers. Therefore, it is necessary to continue the work. The

agricultural use of dredged material brought about a 30-percent increase in

the rice crop by changing badly contaminated water and converting sterile land

to fertile land.

36
ACKNOWLEDGMENTS

The author would like to express great gratitude to the people in the

River Engineering Division of the Prefectural Government, in the Daishoji

Engineering Office, for their cooperation in this work.

37

~4 -24 20
A PILOT STUDY OF DREDGING AND DISPOSAL ALTERNATIVES FOR

THE NEW BEDFORD HARBOR, MASSACHUSETTS, SUPERFUND SITE

M. J. Otis

"1 Army Engineer Division, New England

124 Trapelo Road

AD-P006 454 Waltham, Massachusetts 02254-9149

I 11111 111 ii II~ABSTRACT 111 111 111 

Bottom sediments in New Bedford Harbor are contaminated with polychlorinated biphenyls (PCB) and

heavy metals to the extent that the site is considered

one of the Nation's worst hazardous waste sites and is

being studied by the US Environmental Protection

Agency (EPA) under the Federal Superfund program. At

the request of EPA, the Corps of Engineers has evaluated the feasibility of dredging and disposal alternatives for the upper estuary of New Bedford, an area

where PCB concentrations in the percent levels have

been detected in the sediments. Between May 1988 and

February 1989 a pilot study was performed as part of

this effort. This study involved the evaluation of

three hydraulic pipeline dredges with the contaminated

sediments being placed in a confined disposal facility

and a contained aquatic disposal cell.

This paper provides a comprehensive discussion

of our approach and the results of this $6.5 million

effort. The study provided for a site-specific technical evaluation of the methods used which has allowed

the Corps of Engineers to make recommendations to EPA

which will be critical in their final evaluation of

remedial alternatives for the site.

INTRODUCTION

New Bedford, Massachusetts, is a port city located on the northwest side

of Buzzards Bay, approximately 55 miles south of Boston (Figure 1). Historically, New Bedford is known for its role in the development of the whaling

industry in the 1800's. Today, the harbor is the home port to one of the

largest commercial fishing fleets in the United States (Ebasco Services 1989).

The harbor is underlain by sediments containing elevated levels of PCBs

and heavy metals including copper, chromium, zinc, and lead. PCB concentrations in the sediment range from a few parts per million (ppm) to over

100,000 ppm. PCB levels in harbor water have been measured in the parts per

billion range (Weaver 1982).

38 92-10774

92 4 24 -2- 0
C0o20haI St.

N. Y@% N.. Popes Aus ic Ocean Island

NeNo Bedfor

New Bedford

Hurricane Barrier

Buzzards Bay Sconticut

Point

Ricketsons

Point

Figure 1. Outer New Bedford Harbor

39
The source of the contamination was two electrical capacitor manufacturers who were major users of PCBs from the time their operations commenced

in the 1930's until 1977, when the US Environmental Protection Agency (EPA)

banned the use of PCBs. These industries discharged wastewaters containing

PCBs directly into the harbor and indirectly via the municipal sewer system

(USEPA 1976)

In 1984 the EPA asked the Corps of Engineers (USACE) to evaluate the

engineering feasibility of several dredging and disposal alternatives that

have been proposed for the most northern portion of the site, referred to as

the Acushnet River Estuary. This 200-acre area extends from the Wood Street

Bridge south to the Coggeshall Street Bridge (Figure 2) and contains the

highest levels of contamination. An Engineering Feasibility Study (EFS) was

conducted at the USACE's Waterways Experiment Station which consisted of field

data collection, literature reviews, laboratory studies, and modeling efforts,

and led to the development of conceptual alternatives for dredging and dredged

material disposal (Francingues et al. 1988). The pilot study, which is the

subject of this paper, was an extension of the EFS. It allowed for the verification of design parameters after the laboratory studies were completed and

prior to the final selection and design of a remedial action (New England

Division, USACE 1989).

PILOT STUDY DESCRIPTION

The pilot study involved the evaluation of three types of hydraulic

pipeline dredges and two disposal methods. Approximately 10,000 cu yd of

sediment was removed, 2,900 cu yd of which was contaminated. Both use of a

confined disposal facility (CDF) and contained aquatic disposal (CAD) were

evaluated. Operations were extensively monitored to detect changes in water

quality throughout the harbor that could be attributed to the dredging and

disposal operations while gathering data to address the technical objectives

of the study. These objectives were to

a. Determine if dredges could effectively remove the contaminated

sediment.

b. Evaluate sediment resuspension and contaminant release at the point

of dredging and during CAD.

c. Determine if contaminated sediment could be contained in a CAD cell.

Dredging and disposal operations were conducted in a small cove adjacent

to the channel in the upper estuary (Figure 3). PCB levels in the cove were

150 to 600 ppm in the top 6 in. of sediment and were not detectable below

2 ft. Water depths were 0.5 ft at low water with a tide range of approximately 4 ft. The sediment was an organic sandy silt. The shallow water and

finegrained material are typical of a large portion of the upper estuary.

DREDGING EQUIPMENT

The three hydraulic pipeline dredges used during the study were a cutterhead dredge, a horizontal auger dredge know as a Mudcat, and a modified

cutterhead dredge that has the cutterhead replaced with a Matchbox dredge

head. This equipment was selected after a thorough evaluation by USACE

40
ridg

Brooklawn Pa

Quarries

N

Noil

0 Pilot F-Mri6v n

ite

RTMI 952!

gashall-S.t.-Sr' 9

It R- .T. W . 5

ST

Fairhaven

-73

ast

(--.fopee Island Fairhaven

Fish CmW

island Island

n

New B for

New Beo I-) rd

Harbor

Buzzards Bay

Figure 2. New Bedford Harbor and Acushnet River Estuary

41
CAA

250'

Dredging Area

180'

L

Top of bank +6'

CDF discharge

(400' , D

fDF

IVIMLW

(l Meteorological Station 500' N

® Air Monitoring Stations

Datum: mean low water (MLW)

Figure 3. Pilot study site

personnel that considered a wide range of dredging equipment. The following

factors were considered critical in selecting the dredging equipment:

a. Ability to remove the layer of contaminated sediment while minimizing

overdredging.

b. Ability to minimize resuspension of sediment while operating.

c. Ability to operate in the shallow water which is prevalent in the

upper estuary.

The major operational differences between the dredges were their dredge

heads and their method of moving through an area while dredging. Both the

cutterhead and Mudcat dredges have a revolving dredge head that breaks up and

agitates the bottom sediment. The Matchbox dredge head has no mechanical

action and relies on the swing of the dredge and suction forces to move the

sediment. The cutterhead and Matchbox dredges pivot on their stern spuds and

dredge in a zigzag fashion while pulling on swing anchors. They advance by

alternately raising and lowering the spuds at the end of a swing. The Mudcat

42
operates off a cable system, winching itself along in both forward and

reverse.

During the course of the study, different methods of operating were experimented with while attempting to meet the project goals of removing the

contaminated sediments while minimizing both overdredging and the resuspension

of sediment. Operating parameters that were adjusted included swing speed,

rate of advance, rotation of the cutterhead, and depth of cut.

DISPOSAL METHODS

The two disposal methods evaluated during the study were a confined disposal facility (CDF) and contained aquatic disposal (CAD). The CDF is a

retention basin that was constructed on approximately 250,000 sq ft of area,

half of which was located below the high water line. A granular fill dike was

constructed around the perimeter of the CDF, and it was divided into two chambers by a sheet-pile wall. The dredged material slurry entered the primary

cell where the majority of the solids settled out. The excess water flowed

over a weir built into the sheet-pile wall where a cationic polymer emulsion

was sprayed into the flow to promote additional settling of solids in the

secondary cell prior to discharging the water back into the estuary. Approximately 2,200 cu yd of contaminated sediment was pumped into the CDF and subsequently covered with approximately 3,900 cu yd of clean dredged material.

CAD involved initially dredging a pit or cell in the bottom of the estuary. Approximately 700 cu yd of contaminated sediment was then discharged

through a diffuser into the cell and subsequently capped with approximately

2,600 cu yd of clean material placed in the same manner. The area dredged

during the filling of the CDF was used as the CAD cell. It was approximately

180 by 140 ft in size and 6 ft deep. A 0.5- to 1-ft layer of contaminated

sediment and a 1- to 3-ft layer of cap material was placed in the cell.

USEPA's Environmental Research Laboratory in Narragansett, Rhode Island,

assisted the USACE in designing and executing the monitoring program which

consisted of physical, chemical, and biological evaluations of sediment, harbor water, leachate, and effluent from the CDF. The following were the program's major objectives:

a. Monitor contaminant release pathways associated with the dredging and

disposal operations.

b. Monitor water quality throughout the harbor.

c. Provide data in a timely fashion to assist in managing ongoing dredging and disposal operations.

Four monitoring stations were established throughout the harbor. They

were located approximately 1,000 ft north of the pilot study cove, opposite

the cove, at the Coggeshall Street Bridge and just upstream of the hurricane

barrier. The stations were sampled prior to the start of operations to determine the existing ranges of specified physical, chemical, and biological response variables which occur within the system. The stations were subsequently sampled during the three phases of the project: CDF dike construction, dredging with disposal into the CDF, and dredging with CAD.

43
The Coggeshall Street Bridge station was the focal point of the monitoring effort due to the location (boundary between the more highly contaminated

upper estuary and the less contaminated lower harbor) and the fact that water

circulation is restricted at this point. At this station the flow was measured for each sampling event, and samples from six cross-sectional subareas

were composited proportional to velocity. Equal portions of the five hourly

composites were then combined to form one sample representing either the flood

or ebb tide condition. Samples from the other stations were taken hourly at

three depths. The five hourly composites were then combined into one sample

for each station which represented the ebb or flood tide condition. The results of the preoperational monitoring are summarized below and in Table 1.

Seawater temperature 18.50 - 23.50 C

Salinity 22 - 33 ppt

Total suspended solids 6.4 - 10.2 mg/1 (station 2)

4.4 - 7.9 mg/1 (station 1)

TABLE 1. PREOPERATIONAL MONITORING PERIOD - AVERAGE

CONTAMINANT LEVELS

Station* Tide Total PCB** Cd** Cu** Pb**

I Ebb 1.69 0.33 6.8 4.1

2 Ebb 0.60 0.23 5.5 2.8

4 Ebb 0.12 0.15 2.7 2.2

* Station 1 - approximately 1,000 ft north of work area.

Station 2 - Coggeshall Street Bridge.

Station 4 - Hurricane Barrier.

** Reported in parts per billion.

Contaminant release pathways that were monitored during the operational

phase of the study included leachate movement through the bottom and dikes of

the CDF, effluent discharge from the CDF and airborne releases from the CDF,

sediment resuspension and contaminant release at the point of dredging and at

the discharge point during CAD, and movement of contaminants away from these

operations.

RESULTS

The dredges used during the pilot study were able to effectively remove

the contaminated sediment while minimizing the amount of material removed. By

making two passes over an area, the cutterhead and Matchbox dredges removed

1.1 to 1.5 ft of material leaving PCB levels of less than 10 ppm in the

remaining sediment.

By slowing down the various operating parameters (swing speed, rate of

advance, cutterhead rotation, etc.), sediment resuspension at the point of

dredging was reduced. Resuspension rates and contaminant release at the point

of dredging varied between the different dredges, but impacts 500 ft from the

44
point of dredging were minimal for all dredges. Average values for sediment

resuspension rates, total supsended solids levels, and PCB levels adjacent to

the dredge head are summarized in Table 2. The cutterhead dredge was recommended for future work in New Bedford based on the results of the pilot study.

TABLE 2. SEDIMENT RESUSPENSION AND CONTAMINANT

RELEASE DURING DREDGING OPERATIONS

Resuspension Rate Total Suspended Total PCB

Dredge K/sec Solids, mg/ ppb

Cutterhead 12 82 7.0

Matchbox 46 319 2.6

Horizontal auger 329 1,610 54.9

Notes: 1. Background levels for suspended solids and PCBs are less than

10 mg/i and 0.5 to 1.0 ppb, respectively.

2. The resuspension rate is calculated using the following factors:

water depth, length of dredge head, swing speed, and average

suspended solids in the water column adjacent to the operating

dredge head.

3. Samples used to obtain these data were taken from a sampling device installed at the dredge head. Samples were drawn from six

sampling ports positioned around the dredge head.

An array of 15 stations located around the dredges were sampled hourly

while the equipment was operating. This monitoring effort was carried out to

detect the movement of resuspended material and contaminants away from the

point of dredging. Tidal currents within the cove were negligible (0.1 to

0.3 ft/sec), and a defined plume of resuspended material never developed.

Suspended solids and contaminants were at background levels 500 ft from the

operating dredges.

Contained Aquatic Disposal

The major questions relating to CAD involved the placement of contaminated sediment within the cell, the capping of this sediment with clean

dredged material, and the sediment resuspension and contaminant release associated with the operation.

Hydrographic surveys indicated that a 0.5- to 1-ft layer of contaminated

sediment was placed in the cell and capped with a 1- to 3-ft layer of clean

dredged material. Sediment cores taken from the cell and analyzed for PCBs

showed the capping operation to be unsuccessful, however, as elevated PCB

levels were found in the surface sediment layers. The contaminated and cap

material likely mixed together because of the position of the diffuser and the

fluid state of the contaminated sediments. Because of the shallow CAD cell,

the diffuser was located approximately 2 ft off the bottom, which may have

disturbed the sediment in the area of the discharge. Capping operations also

began immediately after disposal of the contaminated sediment without allowing

45
time for the material to consolidate. The physical characteristics of the

contaminated and cap material are tabulated below:

% Fines Water Content Specific Gravity Liquid Limit

Contaminated 78 159% 2.46 123

Cap 79 117% 2.55 107

An array of 10 stations was established around the CAD cell to detect

any suspended material or contaminants resulting from the operation. This

monitoring effort showed that both suspended sediment and contaminant levels

were elevated well above background and other phases of the pilot study.

Table 3 summarizes suspended solids levels for a typical day of CAD.

TABLE 3. TOTAL SUSPENDED SOLIDS DURING A

TYPICAL DAY OF CAD

Sampling Distance from Total Suspended

Event Discharge, ft Solids. mR/I

1 100 31

300 13

2 100 55

300 26

3 100 49

300 31

4 100 107

300 78

5 100 179

300 117

Notes: 1. Samples were taken hourly with the first sampling event 30 min

after the start of disposal operations.

2. The values shown for total suspended solids represent the average

of five individual samples.

3. Background levels within the cove are generally less than 10 mg/I.

Several composite samples were formed daily from the five individual

stations representing cross sections of the cove. These samples were analyzed

for PCBs. The results show that PCB levels ranged from 2.5 to 31.8 ppb and

averaged 13.4 ppb for the area 100 ft from the discharge point, and ranged

from 1.5 to 15.3 ppb and averaged 6.8 ppb for the area 300 ft from the discharge point. Background levels in the cove range from 0.5 to 1.0 ppb.

46
Confined Disposal Facility

Both the weir between the primary and secondary cells and the discharge

from the facility were monitored during the operation. Samples were taken

hourly and analyzed for total suspended solids. A daily composite was formed

from these samples and analyzed for PCBs and metals. The results of these

efforts are summarized in Table 4.

TABLE 4. CONFINED DISPOSAL FACILITY

Total Suspended Solids Data. mg/1

Daily

Location Average Ran e Number of Samples

Weir 97 35-344 19

Discharge 75 27-152 15

Dissolved PCB Data, usg/

Mean Range Number of Samples

Weir 1.9 0.6-4.3 12

Discharge 1.4 0.3-2.9 11

Particulate PCB Data. uz/1

Weir 9.1 5.2-15.9 12

Discharge 10.7 5.0-19.2 11

These results indicate that the method used to predict the contaminant

load in the CDF discharge (Palermo 1985) produces a conservative estimate at

this site. This method uses laboratory settling column data to estimate the

effluent suspended solids which are then combined with the results of the

modified elutriate test to estimate contaminant loading.

Harbor Monitoring

PCB levels detected at the monitoring stations within the harbor during

the operational phases of the pilot study are compared with preoperational

conditions in Table 5. The Coggeshall Street Bridge (station 2) was the focal

point as the intent was to limit any increase in the movement of contaminants

from the upper estuary to the lower harbor. The levels detected at station 2

did not represent a statistically significant increase above background conditions. These results indicate that the dredging and disposal operations conducted in the upper estuary did not significantly increase the movement of

contaminants into the lower harbor.

47
0 4

Ln %D

C14 cn Cr4 cn -4 04a

bl 00 0 00

00 c r00 0 -

0

1 C4C 40 0 4 0 (D n%.

~r-Ir4 - 0 -4 4 -4 1Cr-4

02 00 0 0)0 00 C

-400 00 0

Cd00 0 00 Lr 00

'-41 0 00 0Dr4r 0 0

-A

:-5 C) 00C 0 00 00

-A 0

O0 00 C 0 00 00

41 41

0 - 4) 4 4

04 ('4 e4 -A 

P4 4J W 04~

0 ,-4V) cc ~

44 po0 V) Lf) r -1 C~j L)0 -f 4-1

4; 4-4 .4- ~ -40 >~ ~ ca a d - CoO a) Un 0i 4-4 41J

.4 4) -'-4 U Ca U) 4-I bO 4 Cd r. :

w) bo $-4 *r-l 0 P- bO ca 0 :j "0 . 4 "- r

1 0 10 IIr.4IU

00' .0 0 .0 o .fl f0 0 ) U Q) -A4

-2 -4' 04aI flq- ,-Jr,. W - bD

w -1

44 L 0) 04- 0NC 0~ -r4 

.9' _ .9' 

.191

48
CONCLUSION

The study obtained site-specific data on the operational characteristics

of the dredges and the level of contaminant release and sediment resuspension

associated with their operation. These data allowed for field verification of

laboratory techniques for predicting contaminant release and have improved our

ability to make estimates for future work in New Bedford. The study also

addressed two major concerns regarding the evaluation of remedial actions for

the upper estuary. It showed that dredges could successfully remove the contaminated sediment from the harbor. PCB levels in sediment remaining after

two passes of the dredge were less than 10 ppm. It also showed that dredging

and disposal operations could be carried out without a significant increase in

the release of contaminants from the upper estuary to the lower harbor. This

is evident from the results of monitoring at the Coggeshall Street Bridge

(station 2) during the various stages of the study (Table 5).

The study, along with previous work performed during the EFS, has

allowed the USACE to make specific recommendations to the EPA concerning

future dredging work in New Bedford. EPA will rely on these recommendations

in arriving at their decisions on remedial actions at this site.

REFERENCES

Ebasco Services Inc. 1989 (Jul). "Draft Final Hot Spot Feasibility Study,

New Bedford Harbor," Portland, ME.

Francingues, N. R., Averett, D. E., and Otis, M. J. 1988. "New Bedford Harbor Superfund Project, Acushnet River Estuary Engineering Feasibility Study of

Dredging and Dredged Material Disposal Alternatives; Report 1, Study

Overview," Technical Report EL-88-15, US Army Engineer Waterways Experiment

Station, Vicksburg, MS.

New England Division, US Army Corps of Engineers. 1989. "New Bedford Harbor

Superfund Pilot Study, Evaluation of Dredging and Dredged Material Disposal,"

Interim Report, Waltham, MA.

Palermo, M. R. 1985. "Interim Guidance for Predicting Quality of Effluent

Discharged from Confined Dredged Material Disposal Areas," Environmental

Effects of Dredging Technical Note EEDP-04-3, US Army Engineer Waterways

Experiment Station, Vicksburg, MS.

US Environmental Protection Agency. 1976. "New England PCB Waste Management

Study," prepared by EPA Region i, Boston, MA.

Weaver, G. 1982. "PCB Pollution in the New Bedford, Massachusetts, Area: A

Status Report," Massachusetts Office of Coastal Zone Management, Boston, MA.

49

! I 7
DEVELOPMENT OF THE HIGH-RATE DEWATERING SYSTEM

OF BOTTOM SEDIMENTS AND WATER BLOOMS

AD-P006 455 Z. Yosio

Science University of Tokyo

Miyakubo 3-35-15,

Ichikawa-shi Chiba Prefecture, Japan 272

R. Sudo, M. Watanabe

National Institute of Environmental Studies

Tsukuba-Gakuen, Ibaragi Prefecture, Japan 305

H. Misumi, S. Huriuchi, H. Okajima

Hitachi, Ltd., Kandatsu 603

Tsuchiura-shi Ibaragi Prefecture, Japan 300

A. Yagi

Ohgawara, Ltd.

Ginza 8-9-15, Chuuou-ku, Tokyo, Japan 104

Y. Nishikawa

Towa Construction Co., Ltd.

Chiyoda 4-5, Chiyoda-ku, Tokyo, Japan 102

ABSTRACT

In the 10th, 12th, and 13th US/Japan Experts

Meetings, it was reported that the synthetic purification system of lakes and ports using the continuousvacuum precoat filter was most effective and economical to dewater and reuse bottom sediments and water

blooms.

For several years, Japan has developed the highrate, continuous-vacuum precoat filter which was more

efficient and economical than the conventional

apparatus.

The findings by the field investigations at Lake

Kasumigaura and Otsuka Pond-Mito city, etc., are reported herein.

FUNDAMENTAL CONSIDERATIONS

Filtration Phenomena

Figure I shows the model of filtration phenomena prepared by Yoshino.

Part (b) of Figure 1 illustrates the model of standard blocking filtration

50

92-10775

92 4 24 2 0 9 Ilii/I//llI//IIillhIII
(a-) (w, f I

Figure 1. Model of filtration

with zinc particles in a dilute suspension deposit uniformly through flowpaths of a filter medium, such as deep filtration in the sand-filter or dewatering by a solar drying bed. Any continuous dewaterer is unsuitable to a

suspension of this kind, owing to the heavy filter medium.

Meanwhile, in the case of cake filtration (Figure la) and complete

blocking filtration (Figure 1c), in which suspended solids are seized at the

surface of a filter medium, some continuous dewaterer may be available, because of the thin filter medium.

Figure 2 indicates the relation between batch filtration and continuous

filtration (prepared by Yoshino). Figure 2 illustrates (a) a batch filtration

process and (b) a continuous filtration process such as the Oliver filter.

One of the controlling factors for the use of a continuous dewaterer is

whether the wet cake formed on the filter medium can be discharged

continuously,

~91 N..._.

I MI I9

Figure 2. Relation between batch filtration

and continuous filtration

Therefore, when suspended solids are very fine and tend to block a

filter medium such as bottom sediments and water blooms, the conventional

dewaterer, i.e., filter press and Oliver filter, cannot be applied, owing to

difficulty of continuous cake discharge.

51
In this case, the continuous-vacuum precoat filter may be the most applicable, because of cleaning of the precoat-cake with an advancing knife by

50 to 100 pm per rotation of drum, as shown in Figure 3.

Figure 3. Continuous-vacuum precoat filter

Filtration Characteristics

Cake Filtration

a. Batchwise filtration.

(1) The relation between filtrate volume V and dewatering

time t , i.e., a filtration curve, may be expressed by a

parabola, as shown in Figure 4, in accordance with the following equation:

t/V = (l/K)V + (2/K)Vm

where

K - 2A2Apgc (1 - mw)/aw~p

- 2A2Apg(l - mw)/Kwpp

- (I - C)3/E3 (l/p.)k(4/x)2

Vm - AR. (I -mw)/awp

Then, the following relation can be derived:

V/t + V./t = [K(1/t) + (Vm/t)21 1/2

(2) Usually, the resistance of filter medium Rm is much

smaller than the specific cake resistance a . Therefore,

the imaginary filtrate volume Vm corresponding to the

52
resistance R. of the filter medium becomes negligible. In

this case, the expression becomes, approximately:

V/t = 2A 2Apg(l - mw)/awpp . t-1/ 2 - K - t-1 / 2

Then, as the filtration time t increases, the filtration rate V/t

decreases in proportion to t-1/2

(3) The slopes of the dotted line in Figure 4 provide a

comparison of the filtration rate of conventional dewatering

methods; the continuous-vacuum drum precoat filter is seen

to be the most effective dewatering technique from among the

conventional processes.

Co.r I tuous VACUUM

rTLATJOII DAZCW r 1 PNC5i USLU frLTRATOII

I FLltnr Auto.oatt (i ter-pregs Presore riltcr Fjjtc" pros3

'x ;/id" i bed

Figue 4 Fitaio uv an-eatrn appa rus

Bloking Filtration Foeplete 

Te Firato charactritics mayre n ereed apsowair Fiuru5si

acr an ithe the tmyb xrse ihtefollowing equation

Co Boi F

Figur 4.iltratochrteitioncurv mand epresed apsowara Fiurus

aor and l im with a e the xrse following equation.

53
dV/dt = b (An' - m'V)/s

-bAn' - kbV

V = (dV/dt)o/kb(l -e kb • t)

t'Ttana kb

V

Figure 5. Complete blocking filtration

As the filtration time t increases, the filtration rate dV/dt

rapidly decreases, as shown in Figure 5, because the filter medium may be

blocked with fine particles such as bottom sediments and water blooms.

APPLICATION OF CONTINUOUS-VACUUM PRECOAT FILTER

Figure 6 indicates the scope of conventional solid-liquid separation

apparatus (prepared by Yoshino).

The shaded portion in Figure 6 illustrates a wider range of application

of the continuous precoat filter over the other dewaterer, i.e., filter press

and super-decanter. In addition, the filtrate is clean, and the wet cake is

low in moisture content.

DEVELOPMENT OF THE HIGH-RATE DEWATERING SYSTEM

OF BOTTOM SEDIMENTS AND WATER BLOOMS

For a long time, the solid-liquid separation technique, especially on

the precoat filtration, has been investigated as follows.

a. Development of the compound filter aid. In order to remove nutrients

such as NH4-N and P04-P in a filtrate, the compound filter aid (mixed

diatom earth with the powder of zeolite, crystbar, etc.) has been

developed.

b. Development of the high-rate continuous-vacuum precoat filter.

Studies on the continuous-vacuum precoat filtration have never been

reported except in our papers.

(1) Figures 7 and 8 show the bench-scale testing apparatus (0.24-m2)

of continuous-vacuum precoat filter set up in our laboratory;

Figures 9 and 10 show the pilot plant (2.0-m 2) constructed on the

site of Lake Kasumigaura.

54
' II A.

I,

0.1 -- U

_ _ _ I I I I ..

0 I0o 200 300 . o0 00 GOO 700 000

WJ, I J/I I

Figure 6. Solid-liquid separation process

(2) Figure 11 shows the improved model in which two flanges are set up

at the both sides of the filter drum, in order to prevent protrusion of precoat cake from the drum and to form a uniform cake.

(Figure 12 shows the conventional type.)

(3) Moreover, we have set up the swing agitator and constructed

several perforated pipes through which the bottom sediments and

water blooms enter into the bottom of a filter tank and uniformly

upflow in the filter tank, as shown in Figures 13 and 14.

(4) When the high-rate continuous-vacuum precoat filter in Figure 11

was compared with conventional type shown in Figure 12, the former

was found to be superior. Figure 15 indicates that the high-rate

type may be the best dewaterer available for the treatment of

55
bottom sediments and water blooms, from both a technical and an

economic viewpoint.

IFeed I.Ink

~Fed Ourma

Slurry I1nI'

IOrumfIIIer

ap a a u (0 24aci~ in2 )e

56FlraePM
LT .- ..... .

Figure 9. Sketch of the pilot plant (2.0-m2 )

At4

Figure 10. Pilot plant (2.0-m2 ) Figure 11. Improved model of the

high-rate continuousvacuum precoat filter

(5-m2)

'am!

-. ,_. 4J. 4 ,J" +/

Figure 12. Conventional type Figure 13. Sketch of the high-rate

filter (2-m2 ) continuout-vacuum

precoat filter

57
Figure 14. High-rate continuous-vacuum precoat filter

58
"Ki - 2--

Figure 15. High-rate continuous vacuum

precoat filter (47-M 2)

59
REFERENCES

Clean Japan Center; Sai-shingenka gi jutsu, Dassui (1981, supported by the

Ministry of International Trade and Industry, Japan).

Hiraoka, M.; Annual Report of Stuies on Sludge Treatwuet (1980).

Hiraoka, M.; Annual Report of Studies on Sludge Treatment (1981).

Hiraoka, M. and Yoshino, Z.; Odei-Shori-Kogaku (1983, Kodan-sha).

Kagaku Kogaku Kyokai; Treatment Process and Apparatus of Sludge (1978 in

Japanese).

Kagaku Kogaku Kyokai; Dassui-shori Gi jutsu Chosa Hokoku (1981, entrusted from

Tokyo Metro.).

Ruth, B. F., Trans. Am. Inst. Chem. Eng., 33, 34 (1937); Ind. Eng. Chem., 25,

76 (1933), 27, 708, 806 (1935); 38, 564 (1956).

Steering Group of Special Project Research on Detection and Control of Environmental Pollution, Supported by the Ministry of Education, Japan; Chemical

Engineering for Water Pollution Control, Vol. 3 (1979).

Yoshino, Z.; KAGAKU KOGAKU, 30, 205 (1966).

Yoshino, Z.; Ibid., 35, 91 (1971).

Yoshino, Z.; Inter. Chem. Eng., ii, 547 (1971).

Yoshino, Z.; Industrial Water, No. 171, 10 (1972).

Yoshino, Z.; KAGAKU KOGAKU, 37, 431 (1973).

Yoshino, Z.; Ibid., 41, 88 (1977).

Yoshino, Z.; KAGAKU KOGAKU, 43, 130 (1979).

Yoshino, Z.; Industrial Water, No. 257, 61 (1980).

Yoshino, Z.; KAGAKU KOGAKU, 45, 89 (1981).

Yoshino, Z.; Ibid., 45, 423 (1981).

Yoshino, Z.; Industrial Water, No. 286, 9 (1982).

Yoshino, Z.; The 10th US/JAPAN Experts Meeting (Oct. 1984).

Yoshino, Z.; The 12th US/JAPAN Experts Meeting (Nov. 1986).

60
AD-P006 456

1Ill1ll IIll 1111111111 fi t 1I I li11 EXAMPLE OF LATEST TECHNIQUES FOR

BOTTOM SLUDGE DREDGING

J. Hamasuna

Member of Engineering Committee

Japan Sediments Management Association

2-7-12 Tsukiji, Chuo-ku, Tokyo 104, Japan

ABSTRACT

Recently in Japan, the biggest problems of the

bottom sludge dredging are lack of enough room for

dumping areas and preventing water contamination during dredging in terms of environmental aspects. The

new dredging system introduced at this time has been

developed fnr the above purposes.

INTRODUCTION

Recently, a bottom sludge dredging technique which permits a low level

of turbidity and a small volume of land reclamation has been required as a

part of muddy water purification works.

Sludge dredges today are mostly centrifugal-pump vessels with special

suction heads. This type of vessel is used because solutions to environmental

problems require dredging highly concentrated sludge in large quantities.

Extensive research and development into pump-type dredges with special

suction heads have also been continued until the present. To suck up bottom

sludge with a low water content, it is fluidized by stirring it to some extent. Then, some external water will begin to flow into the bottom sludge.

Since those portions which are ready to flow are sucked up first, a decrease

in the mean sludge content results.

In addition, expenses for disposing of the extra water produced in

reclamation areas have been increasing in proportion to the sludge content.

On the other hand, there are backhoe-mounted vessels and grab dredges

which are capable of dredging sludge with its natural water content unchanged.

However, they are not very suitable for dredging bottom sludge intended to

improve water quality in terms of environmental quality, because they involve

water contamination, offensive odor, splashes of sludge, etc. Thus, bottom

sludge dredging involves many difficulties, and comprehensive dredging techniques that take careful account of environmental pollution are strongly

desired.

The bottom sludge dredging technique discussed here is a dredging system

developed and applied to dredge bottom sludge in almost its natural state and

discharge it to reclamation sites through pipelines. This paper presents the

61 92-10776 9 2 4 2 4 21o0llitqllllliikil[~iqI
principles and capabilities of bottom sludge dredging (high-concentration

soft-sludge dredging) techniques, some achievements of dredging work, and the

current situation of high-concentration soft-sludge dredging techniques.

OUTLINE OF BOTTOM SLUDGE DREDGING SYSTEM

Principles

The system here consists of a dredging (excavating and sludge collecting) section, a driving section for forcing the collected sludge forward, a

discharging section for transferring sludge to the reclamation site, and an

operating section for controlling all of the sections (Figure 1).

Dredging

A bucket wheel is used for dredging. Sludge is excavated up by allowing

a dredging bucket wheel to run very slowly in a semicylindrical airtight submerged hood (Figure 2).

Bottom sludge is separated from surface water in the airtight hood (air

atmosphere) and taken into a tank. This operation is so slow that it scarcely

stirs the mud and thus permits dredging work to be performed with very little

contamination to the surrounding water areas as compared with conventional

dredging methods using cutter-equipped pump dredges and grab (or backhoe) type

systems.

In addition, the bottom soil in bottom sludge removal work is not always

soft (N 2) but is occasionally harder. Thus, the dredges have auxiliary

excavators.

Discharge

Using this dredging system, bottom sludge is mostly dredged in a deposition state. Therefore, no conventional centrifugal pumps can be used for

pipeline transfer in this case. Thus, an air pressure method is employed.

Sludge is delivered into a discharge pipeline by a compression assisting unit.

In the pipeline, the bottom sludge is mixed with compressed air fed continuously to give suitable plug and slag flows and is discharged to the reclamation site. There are few reports and documents published on the engineering

details of the air-mixed compressed transfer method (for dredged sludge).

Thus, at the present stage, data on proof tests and actual works are used as a

guide.

Operation Control

The present system operates in the same way as conventional sludge

dredges and cutter-equipped pump dredges. Basically, it is a swing-spat type.

The operator can control dredging by observing on the monitor TV (Photo 1) how

the bucket wheel in the airtight hood excavates sludge. The system is also

provided with units for setting dredging locations, widths, etc.

62
Compesse airSwing direction

(Air compression transfer)

0 o Soil to bedredged

Assist unit, stirring and Itransfer Ecvtosug oeto

Figure 1. Sketch of bottom sludge dredging system

Figure 2. Vessel structure

Photo 1. Television monitoring

system

63
Specifications of Bottom Sludge Dredge

Name .......................... High-concentration soft-sludge dredger

Dredging and transfer system. Bucket-wheel excavation, air-mixed compression transfer

Capacity ..................... Soil, soft sludge

Nominal capacity ..... 100 m 3/hr

Discharge distance... 1,000 m (water content w. - 150%)

Dredging depth ....... 10 m below the water

surface

Vessel dimensions ............ 29.5 m L x 8.5 m W x 1.8 m H, draft 0.9 m

Main engine .................. Air compressor 190PS (2-4 units)

Main generator ............... 300 KVA (60 Hz)

Assist unit .................. 75 kW

Pipe diameter ................ 0.35 m

Total weight ................. 200 t

FEATURES OF BOTTOM SLUDGE DREDGER

Sludge Dredged and

Discharged in Near-Deposition State

The earth under the water is excavated by a bucket wheel running slowly

in an airtight hood placed on the bottom so that soft sludge can be dredged

almost as it is deposited.

High-Concentration Sludge Transfer in Pipeline

Soft sludge is mixed with compressed air at a suitable ratio and is

transferred in a pipeline (plug on slag flow), where the water content of the

sludge is lower (wo - 100 percent) than in the case of a conventional

centrifugal-pump system.

Work Control

Dredging is done in an airtight hood. Consequently, it can be observed

on a monitor TV, permitting accurate and delicate dredging control.

Spread of Contamination Prevented

Dredging is done in an airtight hood, causing water contamination to be

generated and spread much less than with dredging systems using cutterequipped pump dredges or grabs.

Less Excess Water

Because sludge is dredged almost as it is deposited and is discharged to

the reclamation site, excess water generated and disposed of in the reclamation area is less than in a cutter-equipped pump dredger system, thus presenting no hazards of secondary pollution.

64
CAPACITY

Dredging Capacity

The present bottom sludge dredging system is entirely new. To present

its dredging capacity, the results of proof tests and data obtained in actual

construction works are used as guide. Since the capacity of the present system depends largely on the quality of soil and obstacles, it is essential when

calculating dredging capacity to recognize the quality of the soil and the

existing obstacles.

The present mechanical system was developed on the basis of dredging

soft sludge (N value : 2). The hardness of the soil and the water content in

particular serve as basic measures of dredging capacity.

The properties (mean values) of the soil used for calculating capacity

are as follows:

(1) N value .................... 0 - 7

(2) Weight of unit volume ...... t- 1.3-1.7 t/m 3

(3) Water content .............. . - 150-50 percent

(4) Quality .................... silt (locally with fine sand

40 percent)

Figure 3 illustrates the nominal capacities. Other parameters are as

follows:

(1) Discharge distance: 1,000 m, pipe gage: 0.35 m

(2) Soil lifted represents measured values (m3/hr) based on N values.

(3) Soil lifted represents soil deposited under the water.

(4) For the soil lifting capacity, nominal capacity q. - 100 m3/hr was

used as a design point.

(5) Air feed (Nm3) was 76 m3/min.

Calculation of dredging capacity was based on the following expression:

Q = qx E x Y x T

where

Q - work capacity (each dredged m3/hr)

q - nominal capacity (Figure 3)

E - field work efficiency (Table i)

- network time ratio (Table 2)

T - operating time

Discharge

Although the standard discharge distance here is 1,000 m, discharging is

possible up to 2,000 m by increasing the air feed (decreasing soil ratio)

though at lower discharge rates. Long-distance discharge is possible using an

additional compressor on the pipeline. Where such compressors should be

65
1.0 _

0.9

t 0.8 - 200

2L 0.7

-~ Design point . 0.6 - 150 >

= 0.5

0.4 - 100 3 0. -

S0.3-

2 (m'/hr) ad. 0.2- 50 qo

0.1

q u ( m ) /' , -/ , I- - I L I I | I 1 2 3 4 5 6 7

N value

Figure 3. Nominal capacities

TABLE 1. EFFICIENCY OF FIELD WORK

Weather Soil thickness, horizontal sitape, location, cross-section shape etc.

Classification Tide A little smaller Small

Wave Right A little scattered Scattered

River flow A little changed Changed

High 1.2 1.0 0.8

Efficiency of Medium 1.0 0.8 0.6

field work (E) Low 0.8 0.6 0.4

Note: First, application categories are determined in accordance with weather, tide, and other

conditions and then efficiency levels are determined by taking all dredging conditions into

account.

TABLE 2. NETWORK TIME RATIOS

Soil thickness, horizontal shape, location, cross-section shape etc.

Classification A little smaller Small

Right A little scattered Scattered

A little changed Changed

Net work time ratio (TI) 0.95 0.90 0.85

66
TABLE 3. JUDGMENT OF MAIN PRESSURE

Specification of pump vessel A little smaller Small

Right A little scattered Scattered

Electric Diesel A little changed Changed

Micropump 0.9m or up 0.9 - 0.4m 0.4m or less

E100 - 250 D100 - 350 1.2m or up 1.2 - 0.6m 0.6m or less

E250 - 500 D350 - 600 1.5m or up 1.5 - 0.8m 0.8m or less

E500 - 750 D600 - 800 1.8m or up 1.8 - 1.0m 1.0m or less

E750 - 1000 D800 - 1350 2.Om or up 2.0 - 1.2m 1.2m or less

located depends on soil quality, discharge distance, pipe gage, air rates,

pressure, etc., and a comprehensive study including economy is necessary. In

addition, under an air-compressor transfer system, with a content soil discharge rate, the discharge distance is correlated with the air rate (the supplied air volume) and is also related to the air pressure. For long discharge

distances, suitable air rates are necessary. This relation can be represented

by the "mix ratio."

Mix ratio R = Soil lifted (kg/min)

Air rate (kg/m)in

With mix ratios obtained beforehar.d for sludge discharge distances (500,

1,000, 1,500, and 2,000 m) on the basis of the discharge pipe diameter, discharge capacities and air rates can be estimated to some extent.

Figure 4 shows the pressure gradient in a discharge pipeline. Under an

air-compression transfer system, there is a stable pressure drop gradient

subsequent to a rapid pressure drop caused before the first plug flow is generated. The pressure drop in the pipeline per 100 m is about 0.1 to

0.3 kg/cm 2.

8 Soil = silt, W = 130%

Capacity = 60 m'/h, pipe gage 0.25m

6

r 4

I I I I l

lO00m 2000m

Pressure gradient

Figure 4. Pressure gradient

67
Plug and slag flows in the pipeline are generated and crushed

repeatedly. Thus, it is difficult to obtain the flow rate in the pipeline

accurately. If sludge is discharged efficiently, the quotient of the soil

lifted (m3/hr) divided by the cross section of the pipeline (M2 ) is generally

0.5 m/sec (flow rate in pipeline meters per second).

Volume Change

When bottom sludge is dredged and discharged, some water is included in

it. In addition, if its water content is low (w. - 100 percent), some water

must be added to it to raise the discharge efficiency. Thus, a certain quantity of bottom sludge dredged increases its volume a little before it is

brought to the reclamation site. The volume change ratio is represented as

follows:

1 + G. x W

VR = , x Wx

where

GS - true specific gravity

W - water content of sludge at reclamation site

WO - water content of bottom sludge

Figure 5 presents a chart for use as a guide to volume change ratios.

3.0 Diagram of volume change ratios

(Where. G.= 2.55)

2. 

a

66

.... -Water - -- • content at rmnucmamat ion tU

Figure~0 Diara 5.i ofvlm hnertiostv

68
Obstacles

Obstacles (pieces of rock, wood, vinyl, and fish nets) within the

dredged material have a great effect on dredging capacity. An important problem is how to remove these from the bottom sludge. The present system incorporates a vibrating screen (7.0- by 5.0-cm mesh) to remove such obstacles.

Such screens cannot deal with large fragments, wire ropes, fish nets,

etc. Thus, it is necessary to use an auxiliary means such as preliminary

cleaning of the work area prior to dredging.

In addition, a selection can be made between returning the obstacles

caught by the vibrating screen to the water bottom and disposing of them on

land.

Disposal of Excess Water

The water content of the bottom sludge discharged to the reclamation

site under the present system is w. - 100 percent or above, and the sludge

is very fluid because it is stirred well.

As the reclamation progcesses, the stacked sludge sinks due to gravity,

causing water in it to come up to the surface of the sludge. This pore water

has been grain filtered, its suspended solids concentration being about

20 ppm. Besides, there are remaining water and rainwater in the reclamation

area. A small-scale water treatment plant is provided to dispose of all of

the excess water.

The calculated quantities of excess water generated by the conventional

system using a cutter-equipped pump dredge and the present system using a

high-concentration soft-sludge dredge are shown in Table 4. In the calculation, the volumes of sludge water lifted were obtained on the basis of the

standard sludge contents for both dredges with a dredging rate of 100 m3/hr,

and the volumes of excess water generated in the reclamation area were

compared.

TABLE 4. VOLUMES OF EXCESS WATER GENERATED USING TWO TYPES OF DREDGES

Volume of Volume of Volume of

Soil Dredging Sludge Excess

Lifted Rate Water Water

Type of Dredge (m 3/hr) (m3/hr)

High-concentration 100 10 125 25

soft-sludge dredger

Cutter-equipped 100 80 1,000 900

pump dredger

69
Achievements of Dredging Work

Between August 1987 and September 1989, the present system dredged and

discharged about 560,000 m3 of sludge.

An example of soft-sludge dredging was carried out in Akita Prefecture

between August 1987 and February 1988. The two vessels used were highconcentration soft-sludge dredges each with a nominal capacity of 110 mn3

/h1r.

Figure 6 is a flowchart of the work.

1, 2 00m

Figure 6. Flowchart of dredging work

Soil Data

Table 5 lists the soil data.

TABLE 5. SOIL DATA

No. RED No. WHITE

Sample No. (Depth) (__m - mn) (mn m)

Grains 4.76 mmn or greater % 0 0

Granule (4. 76 - 2 min) % 0 0 0 0

Coarse sand (2 - 0.42 mmn) % 0 0

F'ine sand (0.42 - 0.74 mmn) % 8 8 8 8

Silt (0.074 - 0.005 mm) %88

C:lay (0.005 min or less) %58 55

Colloid (0.001 min or less) %(20) (17)

Filtrate throughi 2,0(90-pm screeni, wt % 100 100

F ii tratle throuigh 1*20-pmn screen, wt 100 100

F i t. rate throughk'.- p screeni wt 92 9?

Mdx. ain dia) ,i i n 0.2 ().4.)

CP rainl d iain. 111111C) 021 0. 015

3(1 rain 11(1i om. I mu 01 41)U ?

1 P# gra in disin . in

tiiif orifit v (5)1ff i c i erit H

(lIr- ,",i t I'lre coe f t i ci t l t it

S;, o Kr a i s SHc )c iic g,,ra. Lv. (, 2.C

I)i 1.p sait
Records of Dredging

Table 6 gives the achievements of dredging in each zone.

TABLE 6. ACHIEVEMENTS OF DREDGING

Dredging Zone Zone I Zone 2 Zone 3 Total

Soil excavated (m 3) 79,300 125,600 103,000 307,900

Operating time (hr-min) 930-15 1,123-55 936-36 2,990-46

Excavating capacity (m3/hr) 85.2 111.8 110.0 103.0

Soil Volume Change Ratio

Sludge was sampled from the bottom deposit and at the discharge port at

the reclamation site while the dredgers were operating. The weights of the

sludge in the measuring cylinders and the apparent weights of unit volumes

were measured, and the differences in value between the bottom deposit and the

discharge port were converted into earth volume change ratios. Table 7 shows

the actual values of the volume change ratio that were achieved.

TABLE 7. SOIL VOLUME CHANGE RATIOS

Dredging Zone Zone I Zone 2 Zone 3 Total

Soil volume change ratio 1.349 1.253 1.225 1.269

Spill-Water Treatment

The spill water generated by dredging was grain filtered d'e to selfweight consolidation. Thus, there was no need to use chemicals when disposing

of it. To treat with the remaining water and rainwater in the reclamation

area, a spill-water treatment plant was prepared, but it was not needed.

CONCLUSION

The bottom sludgc dredging svstem described is an example of a technique

that was established for dredg ig sludge as it is deposited and discharging it

to a land reclamation site , whi h has been c oTelitionallv Considered to he

di f ficul t.

It i '; ht 1 ieved t 1at this t ecIIIi(II wi I I uh e ul t fo r r ducilig tih total

c o';,t of dr,CdeciC rg alld litld ai.,tion 0 WCtC oikS whilt, t p re;e "vi og t V r viro lhliktl

'7
by preventing water contamination, reducing the sizes of disposal areas, improving soil, and reducing the cost of disposing of the spill water, all of

which are required in dredging and land-reclaiming works today.

72
AN UPDATE OF DREDGED MATERIAL CAPPING EXPERIENCES IN THE UNITED STATES

M. R. Palermo

US Army Engineer Waterways Experiment Station

3909 Halls Ferry Road

Vicksburg, Mississippi 39180-6199 AD-P006 457

there has been considerable experience in the

United States regarding level-bottom capping operations in the New England area and in New York Bight.

These operations involve placement of contaminated

sediments at open-water sites by bottom dumping from

hopper dredges or barges, forming a mound on the bottom followed by placement of a cap of clean sediment.

More recent US capping experiences involve hydraulic

placement of highly contaminated sediments from a

Superfund project in New Bedford, Massachusetts, in

preexcavated subaqueous pits. These sediments were

capped by hydraulically placing clean sediment using a

submerged diffuser. Other recent innovations include

controlled placement of materials in thin layers by

pipeline and from barges, recently accomplished in

Puget Sound. Results from these projects and planned

demonstrations of other capping procedures will extend

capping experience in the United States to a wide

range of project conditions.

INTRODUCTION

When dredged material is placed in open-water sites, there is potential

for both water column and benthic effects. The release of contaminants into

the water column is not generally viewed as a significant problem for dredged

material from most navigation projects. The acceptability of a given material

for unrestricted open-water disposal is therefore mostly dependent on an evaluation of the potential benthic effects. Capping is considered an appropriate

contaminant control measure for benthic effects in the US Army Corps of Engineers (Corps) dredging regulations and supporting technical guidelines and is

recognized by the London Dumping Convention as a management technique to "rapidly render harmless" otherwise unsuitable materials.

Capping is the controlled accurate placement of contaminated material at

an open-water disposal site, followed by a covering or cap of clean isolating

material. For purposes of this paper, the term "contaminated" refers to material found to be unacceptable for unrestricted open-water disposal because of

potential contaminant effects, while the term "clean" refers to material found

to be acceptable for such disposal. Level-bottom capping may be defined as

the placement of a contaminated material on the bottom in a mounded

13 92-10777
configuration and the subsequent covering of the mound with clean sediment.

Contained aquatic disposal (CAD) is similar to level-bottom capping but with

the additional provision of some form of lateral confinement, usually an

existing or constructed depression, to minimize spread of the materials on the

bottom.

Level-bottom capping is a dredged material disposal alternative routinely used in the New England area and New York Bight area in the United

States. Results of these efforts have been reported in previous US/Japan

Experts Meetings (Semonian 1983, Mansky 1984). Level-bottom capping and/or

CAD has also been successfully used for placement of highly contaminated sediments and has been demonstrated or evaluated as an alternative for a variety

of disposal conditions (Truitt 1987a, 1987b; Environmental Laboratory 1987;

Palermo 1989; Palermo et al. 1989).

Improved equipment and techniques for capping are being investigated as

a part of the Corps' Dredging Research Program (DRP), managed by the US Army

Engineer Waterways Experiment Station (WES). Case studies of actual capped

disposal projects are useful in determining the effectiveness of the procedures used and for planning subsequent projects. Recent case studies completed in the United States include hydraulic placement of highly contaminated

sediments from a Superfund cleanup project in New Bedford, Massachusetts, in

preexcavated subaqueous pits and controlled placement of materials in thin

layers by pipeline and from barges, recently accomplished in Puget Sound. In

addition, case studies planned for the near future involve controlled placement of material by a bottom-dump barge at a deepwater site in the New England

area and controlled placement of material from barges for an in situ capping

operation in Puget Sound. The results from these efforts will be used as case

studies in the DRP for developing guidelines for capping under a wider variety

of operational conditions. Descriptions of both the completed and planncd

projects are given in this paper and provide an update of US capping

experiences.

NEW BEDFORD CONTAINED AQUATIC DISPOSAL EVALUATION

The upper estuary of the Acushnet River at New Bedford, Massachusetts,

is highly contaminated by PCBs discharged by industries in the years prior to

the 1980's. PCB concentrations in the sediments range from a few parts per

million (ppm) to over 100,000 ppm. The area was designated a Superfund

cleanup site by the US Environmental Protection Agency (EPA) in 1982.

Conceptual designs of dredging and disposal alternatives were developed

and evaluated for their implementability and potential for contaminant release

(Francingues and Averett 1988, Averett et al. 1989). The alternatives were

field tested during a pilot field-scale test from May 1988 to February 1989

(US Army Engineer Division, New England 1989). One of the five alternatives

investigated included a demonstration of CAD. This demonstration involved

dredging 1,680 cu m of contaminated material from the estuary, followed by

2,980 cu m of cleaner cap material, and placing it in a confined disposal

facility (CDF) on shore. As a result, a CAD cell was created in the bottom of

the estuary where an additional 535 cu m of contaminated material was dredged

from a second area and subsequently capped with an approximate 0.7-m thickness

of clean material. A layout of the dredging areas, the CDF, and the CAD cell

is shown as Figure 1.

74
CAD

250'

Dredging Area

180'L

Top of bank +6'

CDF discharge

400' i.;;. -F0 

.+ ...MLW

( i Meteorological Station t So

() Air Monitoring Stations

Scale 1"=400'

Datum: mean low water (MLW)

Figure 1. Layout of dredging and disposal areas for the

New Bedford, Massachusetts, Superfund Pilot

Proj ect

A major consideration for this project was the potential for contaminant

release to the water column during dredging and placement of contaminated

material in the CAD cell. The dredging was accomplished using small hydraulic

pipeline dredges equipped with cutterhead, matchbox, and horizontal auger

dredge heads. Placement of both contaminated material and capping material

within the CAD cell was acc mplished using a submerged diffuser to minimize

resuspension of material. Water quality in the vicinity of the dredging operation and the CAD cell was extensively monitored during the demonstration.

Both suspended solids and PCB concentrations were elevated above background

levels near the upper estuary. Sediment samples through the cap will be taken

to monitor the integrity of the completed cap and to detect any migration of

contaminants into the cap.

75
CAPPING PROJECTS IN THE PUGET SOUND AREA

Lower Duwamish

Waterway CAD Demonstration

The Seattle District of the Corps conducted a demonstration of CAD in

the Lower Duwamish River near the city of Seattle, Washington, in 1984 (Truitt

1986). This demonstration involved placement of 840 cu m of contaminated

material in an existing depression using a conventional bottom-dump barge.

Three barge loads of clean sand were used to cap the deposit. The release of

capping material from the barges was accomplished by gradually opening the

barge to allow a slower release of the sand, which ensured a more even cap

deposit and avoided displacement of the contaminated material. Electronic

positioning was used for control of the barge locations during the operation.

A cross section of the completed CAD cell is shown in Figure 2.

CENTER OF DUMP

-60

\THIRD CAPPING DUMP

SECOND CAPPING DuMP

FiRS1 CAPPING DUMP

CONTAMINATED MATERIAL

ORIGINAL GROUNOL'NE

Figure 2. Cross section of the Duwamish River CAD demonstration project

The placement operation was monitored for the potential release of

material into the water column. Also, the deposit of contaminated material

and capping material was surveyed to determine the thicknesses as placed.

Cores were taken through the cap immediately after replacement, as well as

after 6, 12, and 18 months. The monitoring indicated that between 4 and

8 percent of the material was released during placement. No movement of contaminants into the cap was apparent after 18 months. Additional core samples

were recently taken at 5 years following completion of the cap, and preliminary results from these cores also indicate no movement of contaminants into

the cap.

One Tree Island Marina CAD project

A second CAD project was completed in the Puget Sound area in 1987

(Sumeri 1989). This project involved excavation of 2,980 cu m of contaminated

material by a conventional clamshell dredge. This material was held in three

barges. Then, 7,190 cu m of clean material was excavated by clamshell and

placed at anothe- disposal site, creating a conical pit. The contaminated

material was then dumped into the pit. Clean material was placed directly

from adjacent areas to cap the pit with a 1.2-m thickness. Monitoring will be

accomplished to verify the integrity of the cap. A cross section of the

project is shown in Figure 3.

76
to

6 CONTAMINATED

"2 1

-2 -

.Z CLEAN

-34 CCEAN FTMCA EDG

-o ' - I~ p LI IT -264

Situ FIn( COaTA INATE FILL -26

DENSE -INVE u30

SAND 5 HARD -38f

sILr 3

-42

-46

Figure 3. Cross section of the One Tree Island Marina

CAD project

Simpson Tacoma Kraft

In Situ Capping Project

The Tacoma, Washington, Harbor and its adjacent Waterways and nearshore

areas are Superfund cleanup sites. The nearshore area sediments at the

Simpson Tacoma Kraft company were contaminated with a variety of organic chemicals. The company performed remedial work to clean up the sediments and

provide source control and restore natural habitat in 1987 (Sumeri 1989). The

remedial work consisted of raising the existing bottom from subtidal to intertidal elevations by capping the contaminated materials in situ. Approximately

153,000 cu m of clean sand was placed as a cap using conventional cutterhead

pipeline dredges. A diffuser box with a spud barge provided for more even

distribution and control of the sand during placement. The cover was placed

in a thin lift by swinging the diffuser box through a wide arc, then advancing

the spud barge. Long-term monitoring of the cap will be accomplished to

ensure its effectiveness. A typical section of the completed cap is shown in

Figure 4.

MASSACHUSETTS BAY DISPOSAL SITE CASE STUDY

T!.e New England Division (NED) of the Corps will conduct a demonstration

of controlled placement techniques at the Massachusetts Bay Disposal

Site (MBDS), formerly the Foul Area Disposal Site, located approximately

22 nautical miles east-northeast of Boston, Massachusetts, in a water depth of

90 m (Figure 5). Dredging will be conducted using standard clamshell equipment with placement from bottom-dump barges. The objective is to demonstrate

that a tight disposal mound suitable for capping can be formed on the bottom

at this water depth by carefully controlling the disposal operation. All

77
-8

-12

VERTICAL EXAGGERATlCN &5 New Elevation

----------- organic Fill Elevation

ELEVATIONS IN FEET" MLLW Eitn lvto

-------- Existing Elevation

Figure 4. Cross section of the Simpson Tacoma Kraft capping project

or* is e0W 070 34000W 070 32+000W

A rLANrtC Oct..4 42 20 00ON

LOCATION MAP

42 25S006N A2 -- 25 004N

CJSPOSAL SirE

SCALE

a00 3009 I0s .009-0 vo 0)0200MW__ -- ..o ... ..... 0

Figure 5. Location and plan for the Massachusetts Bay Disposal Site

capping demonstration project

releases of material from the disposal barges will be within 10 m of a tautline buoy. A successful demonstration will support the technical feasibility

of capping in deepwater locations. The monitoring for -he demonstration will

be conducted as a part of NED's Disposal Area Monitoring System (DAMOS) program (Fredette et al. 1987).

The need to address the question of capping feasibility at the MBDS has

become more urgent because of current project needs and projections that there

will be large volumes of relatively contaminated sediments dredged in the

Boston region in the next several years. The alternative of open-water disposal followed by capping needs to receive serious consideration as it may

78
prove to be economically compelling. Consequently, there is a need to provide

a sounder technical basis on which to judge the technique than that which

currently exists.

The need for such a demonstration stems from the controversy over proposed capping operations in deep water. Placement of dredged material without

excessive dispersion and spread, formatien of mounds which can be successfully

capped, and prediction and monitoring of such behavior are critical issues for

deepwater capping projects which need further investigation (Palermo 1989).

Operational capability must be proven, and predictive capability must be verified for deepwater conditions. The principal concern of capping at deepwater

sites is the impression that large volumes of capping sediment may be needed

to effectively cap relatively small volumes of contaminated sediment.

The MBDS demonstration will be conducted with approximately 45,000 cu m

of sediment suitable for open-water disposal, so no actual cap of cleaner

material will be necessary. This volume was chosen as representative of the

volume expected in future projects. Sediment grain size will also be considered so that it will be representative of future proj cts. A predisposal

bathymetric survey around the location of the taut-wire buoy and baseline

sediment profiling camera data have also been collected. Additional bathymetry and sediment profiling camera data will be collected at intervals during

and following disposal operations for comparison.

The inspectors and tug operations will be thoroughly briefed regarding

the objectives of the study prior to beginning operations. During the disposal operation, all releases of dredged material will be controlled to within

10 m of the buoy. If weather conditions do not permit such control, the

barges will be diverted to a far removed alternative buoy until weather conditions again permit the required control. This precaution will ensure that

all material placed at the study site will be released within the 10-m radius

throughout the study. Electronic positioning equipment will be used to determine the location of the disposal vessel.

The study will determine the areal extent and thickness of the dredged

material deposit formed at the MBDS as a result of the controlled placement.

It is expected that with a 10-m radius of release at the surface, a disposal

mound with a radius of approximately 250 m will be created. The ability to

create a mounded deposit for this project will greatly increase confidence in

the ability to successfully execute capping projects at the MBDS site.

DENNY WAY DEMONSTRATION

The Seattle District of the Corps and the Municipality of Metropolitan (METRO) Seattle, Washington, are cooperating in a demonstration capping

project for contaminated sediments adjacent to the Denny Way Combined Sewer

Overflow (CSO) (Sumeri 1989). A combined sewer overflow is one that discharges both uott~ated sanitary sewage and stormwater runoff, acting as a

relief point d'iring peak storm events so as not to overload the sewage treatment facility. The CSO at Denny Way is the largest in the area and has about

50 overflow events a yea-. Historical discharges of metals and polynuclear

aromatic hydr9carbons (PAIl's) into the sewef system hsve resulted in sediment

contamination in the immcdiate vicinity of the discharge point. A recently

7q
developed CSO control plan and source control activities will greatly reduce

future contaminant loadings.

The Denny Way demonstration will involve placement of a sand cap over

the contaminated sediments as shown in Figure 6. A unique method of controlled placement is proposed to place the desired thickness of cap over the

contaminated area. The sand capping material will be taken from a Corps maintenance dredging project. Conventional clamshell equipment will be used to

dredge the material and place it in bottom-dump barges. The cap will be

placed at the Denny Way site by pushing the barge sideways while sprinkling a

39-m-wide blanket of sand over the bottom. The sprinkling action will be

accomplished by controlling the rate at which the split-hull mechanism of the

disposal barge is opened. Two radio tide gages with pressure transducers

located in stilling wells at each end of the disposal barge will be used to

measure barge displacement, which is subsequently used to determine the sand

sprinkling rate. A shore-based laser positioning system will track the barge.

The barge positi,rn and displacement data are to be telemetered to the attending tug. The onboard monitor screen will show the intended barge course,

actual barge position, and the sand sprinkling rate. In this way, the speed

of the barge and thus the rate of application of sand can be adjusted as the

bargu is moved across the area to be capped. A 0.9-m cap is planned. METRO

will conduct future testing of the cap effectiveness. The study will demonstrate the feasibility of using this approach and will provide information on

material placement rates, optrational logistics and problems, and cap coverage

obtained for the project.

D ENNY' WAY CSOJ

ELtiOrr &A r

S SEAT TLE

APPROX - 60'

DEPTH

LOCATION MAP

APPROZIMATE AREA

TO BE CAPPED--- I

PIER 71

\\ / --- 3" TIDE LINE

SCALEMYRTLE EDWARDS PARK

200 • 200 400 FT

Figure 6. Plan for the Denny Way capping demonstratio-n project

80
SUMMARY

A sufficient number of capping projects have been completed in the

United States under a range of conditions to establish that the concept is

technically and operationally feasible. The information gained in the

recently completed projects and planned projects described above will be used

in developing Corps guidelines for capping under a wide variety of conditions.

ACKNOWLEDGMENT

The information presented in this paper is based on studies conducted by

the US Army Engineer District, Seattle, and the US Army Engineer Division, New

England, and on research conducted by the US Army Engineer Waterways Experiment Station under the Dredging Research Program. Permission was granted by

the Chief of Engineers to publish this information.

REFERENCES

Averett, D. E., Palermo, M. R., Otis, M. J., and Rubinoff, P. B. 1989. "New

Bedford Harbor Superfund Project, Acushnet River Estuary Engineering Feasibility Study of Alternatives for Dredging and Dredged Material Disposal;

Report 11, Evaluation of Conceptual Dredging and Disposal Alternatives,"

Technical Report EL-88-15, US Army Engineer Waterways Experiment Station,

Vicksburg, MS.

Environmental Laboratory. 1987. "Disposal Alternatives for PCB-Contaminated

Sediments from Indiana Harbor, Indiana; Volume 1," Miscellaneous Paper

EL-87-9, US Army Waterways Experiment Station, Vicksburg. MS.

Francingues, N. R., and Averett, D. E. 1988. "New Bedford Harbor Superfund

Project, Acushnet River Estuary Engineering Feasibility Study of Alternatives

for Dredging and Dredged Material Disposal; Report 1, Study Overview,"

Technical Report EL-88-15, US Army Engineer Waterways Experiment Station,

Vicksburg, MS.

Fredette, T., Morton, R. W., and Germano, J. D. 1987. "Aquatic Dredged Material Disposal in New England," Proceedings of the Conference Coastal Zone 87,

American Society of Civil Engineers, Seattle, WA.

Mansky, J. 1984. "Capping of Dredged Material Disposal Management for New

York Harbor," Proceedings of the 8th US/Japan Experts Meeting on Management of

Bottom Sediments Containing Toxic Substances, US Army Engineer Waterways

Experiment Station, Vicksburg, MS.

Palermo, M. R. 1989. "Capping Contaminated Dredged Material in Deep Water,"

Proceedings of the Specialty Conference Ports 89, American Society of Civil

Engineers, Boston, MA.

Palermo, M. R., et al. 1989. "Evaluation of Dredged Material Disposal Alternatives for US Navy Homeport at Everett, Washington," Technical Report

EL-89-1, US Army Engineer Waterways Experiment Station, Vicksburg, MS.

81
Semonian, R. C. 1983. "Studies on Capping of Contaminated Dredged Material

in the New England Division," Proceedings of the 7th US/Japan Experts Meeting

on Management of Bottom Sediments Containing Toxic Substances, US Army Engineer Waterways Experiment Station, Vicksburg, MS.

Sumeri, A. 1989. "Confined Aquatic Disposal and Capping of Contaminated

Bottom Sediments in Puget Sound," Proceedings of the WODCON XII, Dredging:

Technolopy. Environmental, Mining. World Dredging Congress, Orlando, FL,

2-5 May 1989.

Truitt, C. 1986. "The Duwamish Waterway Capping Demonstration Project:

Engineering Analysis and Results of Physical Monitoring," Technical Report

D-86-2, US Army Engineer Waterways Experiment Station, Vicksburg, MS.

Truitt, C. 1987a. "Engineering Considerations for Subaqueous Dredged Material Capping - Background and Preliminary Planning," Environmental Effects of

Dredging Technical Note EEDP-01-3, US Army Engineer Waterways Experiment Station, Vicksburg, MS.

Truitt, C. 1987b. "Engineer,1 g Considerations for Capping Subaqueous Dredged

Material Deposits - Design Concepts and Placement Techniques," Environmental

Effects of Dredging Technical Note EEDP-01-4, US Army Engineer Waterways

Experiment Station, Vicksburg, MS.

US Army Engineer Division, New England. 1989. "New Bedford Harbor Superfund

Pilot Study: Evaluation of Dredging and Dredged Material Disposal," Interim

Report, Waltham, MA.

82
TREATMENT OF DREDGED SLUDGE BY MECHANICAL

DEHYDRATION

T. Maekawa

Japan Dredging and Reclamation

Engineering Association P006 458 2-8, Toranomon 1-Chome,

t!Ui II~ I II Ill I~II HI[I iii ifll Minato-ku, Tokyo, Japan

ABSTRACT

Sludge deposits in the water area damage the

ecosystems and environments; their elimination has

always been an urgent task for human communities.

Generally, sludge deposits are dredged out of the

bottom of the water area, transported to, and discharged at a large disposal area on land. Recently,

however, it has become increasingly difficult to secure disposal areas and routes of speedy transportation for disposal of dredged sludge. Accordingly,

there is &n urgent need to reduce both the volume of

dredged sludge and the size of the disposal area.

This mechanical method is different from the

conventional engineering dehydration by loading, consolidation, and drainage in that the dredged sludge is

separated into sludge cakes and clean water that can

be returned to the water area through mechanical centrifugal dehydraLion. Sludge deposits are distributed

thin and wide on the bottom of the water area, and a

pump dredge has been proved effective in many cases

for dredging the upper layers of sludge deposits accurately and without creating turbidity in water. This

mechanical sludge treatmunt technique can be most

efficient when used in combination with a pump dredge.

This method offers the following advantages:

a. It requires smaller space for treatment and disposal of dredged sludge

than the conventional method.

b. Facilities and costs for transportation can be reduced.

c. Various systems can be adopted for

transportation of sludge cakes.

d. This system is transportable and

compact and can be constructed anywhere either on land or on water.

83 92-10778

92 4t 24 .
INTRODUCTION

The closed water area such as a lake, pond, river, or moat is liable to

accumulation of sludge due to the load of wastewater flowing in from the

plants and residences in its surrounding area. Such sludge deposits pollute

water and environments, and projects are going on or under planning throughout

Japan for elimination of accumulated sludge.

Generally speaking, sludge is removed from the bottom of the river or

other bodies of water by dredging and transferred to the disposal area on

land. However, since it has become increasingly difficult to find an area for

sludge disposal near the working site, a new system to carry out the sludge

disposal with smaller space has been required. In this connection, a mechanical dehydration system has been considered as one of the effective solutions.

This system has been frequently used in disposir- sludge originating

from sewage, purification of water, wastewater from factories and mines, but

its capability and applicability for disposal of accumulated sludge have not

been fully ascertained yet.

To examine the applicability of the system for accumulated sludge disposal, a screw-decanter type centrifugal dehydrator was selected from among

many types of dehydrators, under the judgement that the machine can not only

save the working space but also treat a large quantity of sludge. During the

process of experiment, peripheral units have been added to develop a plant

system which can fully display centrifugal features of the machine.

This report introduces an outline of dredging techniques which form the

basis for sludge treatment aimed at the improvement of water-area environments, as well as the features and samples of application of the mechanical

dehydration treatment.

SLUDGE TREATMENT AND DISPOSITION

Characteristics of Sludge

Sludge deposits are classified into organic sludge, which contains a

large volume of organic matters; poisonous sludge, which contains poisonous

matters; and greasy sludge, which contains oil. Sludge deposits, which are

the target of elimination efforts in many regions, are overwhelmingly organic.

Characteristics of organic sludge are assessed by ignition loss, COD

(chemical oxygen demand), sulfide, nitrogen, phosphorus, and other index

items, and the quantity of each item is very large. Other features include

high water content which makes the sludge soft and fluid, small soil-particle

specific gravity, and the main components of fine soil particles such as silt

and clay. Table I shows the results of a study on characteristics of sludge

deposits in vdrious regions.

Distribution of sludge deposits, on the other hand, has different histories and features including thickness in different locations. There is a

general tendency, however, that the upper layers contain more organic matters.

Figure I indicates samples of sludge-deposit depth distribution.

84
TABLE I. CHARACTERISTICS OF ORGANIC SLUDGE BY REGION

1 2 3 4 5 6 7 8 9 110 11 12 13 14

Region - - -.. . . . . . . . . .

Item ~ 15I asu I 1 ~ 0 A

Mud cologr scrDS ay Dack Dark Deck farS 2. bak rk

Specific gravity I.m 1251 125 L5 t63 2.60 1572 1266 261 z112 Z29 .613 57 Z.5611 2Z 1wZ 5

Gravel. (more

than 2,OO0i) 0 0 0 0 0 0 0 0 0

40 Sand (2,000 

1 S4.}7 4Z.4 10 4L0 IZO 12 a5 SO 25.4 28

4741L)

4.9 -a _ ------

Q-4

.v Si1t (74 - 51&) 3D 142 3LO 5.0 .4 - 71.2 MO 34.1 36

',42

clay (less

than 51) 63 47.4 640 410 210 49 M 0 410 40.5 38

0Water content SWateon54 387.8 151 1940 4X1 187.0 43&8 26&.9 3% M3 1.4 30.4 194.1 32 2L2 1M.3

0 ratio (6)_ -- - - - - - - - - - - - - -- ,,4

$4 LOS Moisture density L133 L 3 0 L 122 L106 L119 L194 L 047 L32 L leg 1.3 L161 L12 L334 0 (g/cm3) -L

10U SLiquid limit 144.7 IX 5 67.0 2R821.01 156 2K83 ZM3 MT2 2X.3! IM15 12L. I8n1 216.5 X5

U C

I n Plastic limit 1 737 815 O1 121.8 4.4 51 1317 L 44.6 .9 9 43 .7 9 96.1 317

waer method --. 5 7.3 9.1 7.8 1 7 7. S0 7.6 57.1 113 22

Kcl solution

method 6.3 177 7.6 7.5 7.75 7.71

Ignition loss 16.11 17.0 '7.9 64.5 21.9 14.5 37.6 1L9 17.6 ?7.1 16.0 11.57 14.1 317 14.1

Organic matter 831.

content (613 1(1

Nitrogen SM 16DO 100 15,9 5614 6290 3000 20 E10 3800 & 3MO

(mg/kg)

Phosphorus 7 3,73 310 5=C 120 1020 431 540 1200 86 l 24

(mg/kg) I31

SulfideSulfid e_.1 04 0.0 0. 17 2.28 L27 6.8 11 - 4.8 1.4 L 78

(mg/kg)

m m ram mmmnmmumim in i i iN 85
Water content ratio Ignition loss T -

0 200 4009 0 20 40,%60 1000 2000t/k '" . a * p p a * I | a a

Intrusion resistance COf T - P

Soil color 0 0.5 1.0 kg.cd 0 20 40/z 0 560 1000/kg

Dark bedGO , ,

material 9

0.1 - loss'

arkish 0.2 resistance /

ray eitnc Dn

bei . IWater material 03 content T - P ratio /

777// 0.4 j T N

alluvial I

silt 0.6 -

0.711 / I I

0.8m

Figure 1. Example of sludge deposit distribution

Systems of Treatment and Disposition

Methods of sludgc treatment and disposition include such main systems as

dredging treatment and reclamation disposal. Subsystems of reclamation disposal include condensation, dehydration, and solidification. These systems are

classified in Table 2.

Sludge Dredging Technology

Problems of Sludge Dredging

Sludge dredging and disposal require continuous work processes of dredging, transport, disposal, and treatment of residual water. For adoption of

one dredging method, therefore, its impact on subsequent processes should be

taken into consideration. Major points for examination about dredging are

listed in Figure 2.

Of the points listed in Figure 2, those specially required for sludge

dredging are as follows:

a. Dredging of surface-layer sludge.

(1) Sludge deposits have a tendency to spread thin and wide. At

places where the deposits are thick, the removal of surfacelayer sludge (containing more pollutants) by sweeping has been

often considered in expectation for internal load reduction

capacity of water and for cost considerations.

86
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turbidity volume

0

0 Noise Water depth C

0

Dredging

0 tthickness

Figure 2.Pobeslfsudedrdi ge

b. Accuacyaof redging

c content

H

- Outbreak

thickn esidual water r

sTrslpft

distance

-disnsaredging

period transpor

Figure 2. Problems of sludge dredging

(2) The target layer of sludge dredging, therefore, is thinner than

that of conventional dredging, and the development of technology for surface-layer dredging is required.

b. Accuracy of dredging.

(1) What is handled in sludge dredging is the deposit of sludge

harmful to the environment. It is necessary, therefore, to

completely satisfy the dredging standards specified for the

thickness of sludge to be removed and other items. Furthermore, high accuracy in dredging is required in handling of tht:

soft muddy bed and eliminating the possibility of leftovers.

88
(2) It is also required to minimize excess excavation in order not

to remove a larger volume of earth than planned, because of the

difficulty of securing disposal yards, as mentioned below, and

other problems.

g. High-efficiency dredging. It has become difficult in recent years to

secure areas for disposal of dredged earth and sand. High-efficiency

dredging is required, therefore, to reduce the size of a disposal

yard and the volume of dredged earth for more effective treatment of

residual water and for quick rearrangement of the work site after

dredging.

d. Countermeasures for turbidity. Occurrence of water turbidity poses

problems for engineering works in water areas. Fine particles of mud

on the bottom of water bodies are handled in sludge dredging, and

dredging technology that can minimize or eliminate the creation of

turbidity is required.

Classification of Sludge Dredging Technology

Improvement of traditional dredging technology and development of new

technology and development of new technology have been under way in order to

meet environmental requirements accompanying the removal of sludge deposits

from water areas.

Classification of dredges and equipment used for sludge dredging is

shown in Figure 3.

Evaluation of Sludge Dredging Technology

Basic functions of dredging are excavation, removal of mud, and discharge. Sludge dredging has an additional requirement (such as dredging of

surface-layer sludge, accuracy of dredging, and prevention of turbidity). In

order to meet these requirements, the methods of dredge operation should be

improved, and a variety of equipment for management of dredging work must be

prepared. A comprehensive system of all these functions is necessary for

sludge dredging. Evaluation of various dredging methods as shown in Figure 3

has been made on the basis of their functions and problems, and the result of

the evaluation is shown in Table 3.

Generally speaking, the pump dredging method, which has been adopted in

many types of dredges, is more suitable for sludge dredging than the grab

dredging method, as discussed below.

a. Measures for surface-layer dredging and accuracy.

(1) Cutter pump dredgers have been used in many dredging projects.

In the case of this type of dredge, the size of the cutter determines the thickness of dredged earth and the accuracy of

dredging. Its swing system makes sweep dredging possible,

leaving the bottom comparatively level after dredging.

89
nDrag-suction dredger 

Special sludge pump d -edqer

Withspca

) het tr dredging, h era i dredger a t

ling a thin layer of sludge. To solve the problem, the cutter

was taken off the pump dredge and replaced by a special suction

equipment for more effective utilization of the dredge's earth

thickness control equipment and swing system for dredging the

thin laer of sludge accurately, as well as for minimizing water turbidity.

90
-4

a 0 0 0 x x

a r a 0 0

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91
(3) Grab and backhoe dredging methods, on the other hand, rely on

the batch system of pit excavation and are not suitable for

surface-layer dredging. These methods also leave the bed

ragged after dredging and have problems in accuracy of work.

b. Measures for high-efficiency dredging.

(1) Some pump dredges adopt special pumps that have greater

capacity of mud suction when compared with conventional

centrifugal pumps. These dredges also use the air-pressure

discharge system capable of comparatively long-distance transportation of high-density slurry in order to maximize the mud

suction capability of special pumps.

(2) Grab dredges, on the other hand, are highly efficient in dredging but have problems in accuracy and creation of water turbidity. Closed-type grabs take in more residual water than opentype grabs, and these require additional measures for water

draining.

c. Countermeasures against occurrence of turbidity. Pump dredges are

remodeled from cutter type to cutterless type equipped with special

suction inlet; grab dredges are remodeled from open type to closed

type, in order to control the occurrence of water turbidity during

dredging work.

Sludge Dehydration Technologv

Dredged sludge is generally transported to a disposal site established

near the dredging site and utilized as materials for a variety of purposes as

shown in Table 4, even if its property is not good.

A disposal site that receives dredged sludge directly may become a final

disposal area or play the role of an intermediate treatment area when there is

a final disposal area set up elsewhere.

Since sludge dredging works in recent years are suffering from an acute

shortage of sludge disposal sites, and more frequent use of intermediate

treatment sites, reduction of the volume of sludge, and other methods are

under intensive study. To attain these goals, the sludge dehydration technology including the drying bed method is believed to play the most important

role.

The dehydration technology is classified into mechanical dehydration and

engineering dehydration, with further details shown in Figure 4.

MECHANICAL DEHYDRATION METHOD

Outline of Method

This method of dehydration by machinery is different from the engineertng methods of surcharge, consolidation promotion, and drainage. The mechanical dehydration system consists of a combination or combinations of machines

92
TABLE 4. DISPOSAL OF DREDGED SLUDGE

Disposal Feature Treatment

Reclaiming disposal (both

in water area and on

land)

Development of parks, 0 Suitable for large- After application of

athletic grounds quantity disposal. engineering dehy0 In the case of noxious dration or chemical

sludge, pollution by solidification,

oozing out should be cover it with goodprevented, quality soil of

about I m thick.

Development of indus- 0 Suitable for large- (Same as above.)

trial and residential quantity disposal.

areas 0 The ground should be

firmer than in the

case of parks and

athletic grounds.

* In the case of noxious

sludge, pollution by

oozing out should be

prevented.

Development of farming 0 Suitable for large- Prepare the soil for

land quantity disposal. planting after

a When large quantities application of

of organic matters engineering

are included, initial dehydration.

fertilization is not

necessary.

* Noxious sludge is not

suitable.

Additional soil to farming (Same as above.) Prepare the soil for

land planting after

application of air

drying, drying bed

dehydration and

engineering hydration in heaps of

about 10 cm.

Material for embankment 8 Suitable for sludge Drying bed dehydraMaterial for roadbed containing less tion, or chemical

organic matters. solidification.

* When used with high

water content, later

contraction may pose

a problem.

93
TABLE 4. (CONCLUDED)

Disposal Feature Treatment

0 In the case of noxious

sludge, pollution by

oozing out should be

prevented.

Material for backfilling (Same as above.) Fill in the soil in

slurry condition

after adding solidification agents.

Vacuum filtering (belt filter, etc.)

Mechanical Pressure dehydration (filter press, etc.)

dehydration Centrifugal separat on (screw decanter, etc.)

Pelletizing dehydration (dehydrum, etc.)

Lother methods

- Nturaln Drying bed method

Continuous trench method

3ngLaeering Base drying method

dehydration Double-faced drying method

Surcharge

- method Surcharge banking metho4

Atmospheric pressure (vacuum method:

Consolidation

- promotion Sand drain method

method j_ Pack drain method

E Paper drain method (chemical drain)

Drainage

method-r--- Well point method

Dep well method

(used concurrently with other methods)

Figure 4. Dehydration methods

and equipment, is transportable, and requires a smaller space than engineering

dehydration methods. Figure 5 presents a flowchart of the processes of this

treatment system.

What plays the central role of the mechanical system is a dehydrator.

Thus, the first step in the development of this method was the selection of a

most appropriate dehydrator. As a result and as shown in Table 5, adoption of

a centrifugal dehydration system was decided in view of the space required for

its installation, continuity, and dredging capacity. The centrifugzil

94
PUMP DREDGER p

CLEAR UPPER WATER DISN TRNSE PIP

DUST4 DICRG E PP

OUST ELIMINATOR LINE MIXER

~DECANTER

PAC SAND DISCHARGE

SOLID CAKE DISCHARGE SEPARATED WATER RECOVERY VIBRATING FILTER . CYCLONE

RAW WATER TANK

Figure 5. Treatment system flowchart

dehydration system, however, had been adopted in a few cases of engineering

works in the past, and many experiments were necessary to ascertain the performance of this system. Finally, a system consisting of a centrifugal dehydrator and auxiliary, peripheral equipment has been developed as a plant which

can maximize the capacity of the centrifugal dehydrator.

System Apparatus

Dust Eliminator

This equipment continually removes pieces of wood, vinyl, or polyethylene 6ottles and other dusts from slurry. Removed dusts are carried by a

belt conveyor installed underneath the eliminator to a garbage yard or a

hopper. This eliminator is used to remove coarse rubbishes and prevent choking of the duct system of the treatment plant.

Vibrating Filter/Cyclone

The equipment is used to eliminate sand from the slurry which contains

soil particles and liquid only after elimination of dusts. This combination

of a filter and a cyclone is installed over the top of a water tank. First,

coarse sand is sieved out by rough meshes of the filter, and the slurry now

containing fine sand, silt, and finer particles only is dropped into the water

tank to be sent to the cyclone by an underwater r'unp. The liquid cyclone by

its centrifugal force separates the slurry into two parts, one containing silt

95
TABLE 5. DEHYDRATORS

Cake

Me wter Filtrate Iatallat- Productia COOCLltr Operation Rough sketch

content turbidity Lon space vlue

DestevLag

Ultiste cutlet ,

.0--

Xlgh Xediu, Large Large Yes GOod Cak

PAl wae• ~ rt ufc

WLIter cloth Jydgau.LU llder

Cak

Separated liqud duct.

0

C

pres cl-l. ,filte.r

.olid Cake

Filtlt Cl nsa eae

1.-.6.

o

High MedLum Small Large Yes Good

I Cake r&.*I Inq

Separated liquid tank

96

C
and finer particles and the other containing fine sand. The slurry containing

silt and finer particles overflows into the raw water tank. The slurry

containing fine sand is filtered through finer meshes of the filter, and the

fine sand particles sieved out are discharged. Sand particles are separated

and discharged in order not to damage the centrifugal dehydrator (decanter),

which is designed to dehydrate silt and finer soil particles.

Raw Water Tank

This tank is used to temporarily store the slurry overflowing from the

liquid cyclone. The stored slurry is pumped out to the thickener.

Thickener

This equipment will separate the slurry sent from the raw water tank

into clear water and the sludge formed by flocks of soil particles. The separation is done by the addition of flocculant (inorganic and high-polymer type)

to the slurry. As the addition of inorganic flocculant acidifies the slurry,

the pH-adjusting agent is also added. Upper clear water satisfying discharge

standards is discharged. Sludge settling down on the bottom of the thickener

is assembled in the center of the bottom by a sludge scraper and sent to the

centrifugal dehydrator by a sludge pump. The basic principle of mechanical

dehydration is sedimentation of soil particles. The higher the density of

slurry by natural settling before separation by a centrifugal dehydrator, the

lower will be the water content ratio of the solid cakes and the cost.

Centrifugal Dehydrator

This machine will separate the slurry of high density into liquid and

solid cakes of silt by the centrifugal effect of high-speed rotation. To

promote the effect of dehydration, high-polymer flocculant is added to the

slurry again at this stage.

The structure of a screw-decanter type centrifugal dehydrator is shown

in Figure 6.

Driving pulley Dewatering zone Liquid zone

For ball

For screw- - Slurry supply

Reduction gears Solids Screw Ball Clean liquid Check plate

discharge outlet

Figure 6. Cross section of screw decanter

A screw decanter is structured to continually separate the liquid with

solid particles suspended in it (slurry) into the liquid and solid portions.

97
A container (bowl) consisting of cylindrical and conical parts and a screw

conveyor positioned coaxially inside the bowl rotate in high speed with a

small difference of speed, while the slurry is continually supplied into the

bowl. The slurry, pushed by centrifugal force, forms a circular pool inside

the bowls, and the solid particles suspended in the pool settle outward away

from the center to reach the inner wall of the bowl.

The screw conveyor carries these solid particles on the inner wall to

the conical part of the bowl, scrapes them up from the pool, and discharges

them out of the decanter after further dehydration. At the same time, upper

clear water separated from the slurry flows out of the bowl over a barrage at

the end of the bowl.

Basic Characteristics

In order to examine the applicability of the mechanical dehydration

method to the dredged slurry of sludge deposits, various experiments using the

dehydrator were conducted to ascertain its performance, together with laboratory centrifuge experiments conducted to investigate the conformity of the two

sets of experiments.

The flow of the procedures of these experiments and the evaluation of

their results is shown in Figure 7, followed by the description of basic characteristics obtained through the experiments using the dehydrator.

Test conditions included factors related to dehydration of dredged

slurry such as mechanical factors (centrifugal effect, speed difference, pool

depth), discharge, kinds of flocculant (PAC, polymer), and the volume of flocculant addition. The results of these tests show trends of the water content

radio of solid cakes and suspended solids (SS) concentration of separated

water.

Details of the test conditions are shown in Table 6, and basic characteristics of the water content ratio of solid cakes and the property of separated water are shown in Table 7.

Centrifugal Effect

The higher the centrifugal effect is, the greater will be dehydration of

solid cakes. Cleanness of separated water reaches its peak at 1,500 G. As

shown in Figure 8, solid cakes are scraped up and carried forward by the screw

conveyor against centrifugal force. A greater centrifugal effect, therefore,

prompts the separation by sedimentation but hampers the transportation of

cakes at the tapering part, rendering adverse effects on the property of processed water. In view of the above consideration, it is judged that the appropriate centrifugal effect for the slurry tested this time is 1,500 G.

Difference of Speed

The smaller the difference of speed is, the better will be the property

of processed water, but the peak of the improvement comes at about 15 rpm.

The property of solid cakes also improves as the difference of speed

decreases. When the difference decreases below that limit, however, the power

98
Centrifugal Centrifugal

effect effect

0 ifreta Residence time

-4 speed

41 rlocculating

o Discharge agent

.. Pool depth 48

rlocculating Sample soil

agent

RAw, water

concentration~

on-itsaednatrationest

Stldd oak aplcblt toatgneein

*Peroct

charcteistis o sepratdiwtinr chrctrstc oifl seroatedems

Figure . Flowo-it mcanclbaor dehyrtio ts

99
TABLE 6. TEST CONDITIONS

Test Condition Numerical Value

Centrifugal effect (G) 1,000, 1,500, 2,000

Differential speed (rpm) 10, 12, 15, 18.9

Discharge (m3/hr) 4, 5, 6, 8, 10

Pool depth (mm) -0.8, 0.125, 0.8, 10

PAC addition (ppm) 150, 300

Polymer addition (%/DS) 0.075, 0.15, 0.3

TABLE 7. TEST CONDITIONS AND TRENDS OF SLUDGE

CAKE/SEPARATED WATER CHARACTERISTICS

Test Sludge cake Separated water

condition Water content SS Trend

The higher the centrifugal offect,

- the better the dehydration of cakes.

SThe volume of suspended matters shows

4 4 the beat value at 1,500 G and

-41 indicates no marked changes at higher

'-Ibu Utr hvlueofsspned 

0 _ -- G levels.

0 (

4 

V) 20 ----

0 Centrifugal 20 0 Centrifugal 20

effect (G) effect (G)

350 -S- The smaller the differential speed,

the better the dehydration of cakes;

* - - -but the volume of suspended matters'

4- indicates the best value at 15 rpm.

- - - r ~ - The trend is conspicuous in the range

-4 0 4 fromi15 to 20 rpm.

4

'44 200 -0 -4 Differential 20 0 Differential 20

speed (rpm) speed (rpm)

100
TABLE 7. (CONCLUDED)

rTest Sludge cake Separated water

condition Water content SS Trend

3 5 Changes in discharge have no impact on the water content of cakes and

--- - the volume of suspended matters.

IT 41

t a 0

o $4g

a 0 0

0DI 00 10 02

Discharge (m3 /h) Discharge (m3 /h)

The deeper the pool, the worse the

-5 dehydration of cakes but the better

- - - the quality of processed water.

41 -

4-41

-4 0 U -

0 j

o 0 -- - 01 

-1 4 -1 4

Pool depth (mn) Pool depth (mxa)

350 Dehydration of cakes is better at

7 -300 ppm of PAC but the change

- - - in PAC pp, figures has no marked impact C on the volume of suspended matters.

-4 : 1 - - -,-

4

20 300 300

PAC (ppm) PAC (ppm)

350 - - - Dehydration of cakes shows the best

value at the range of 0.3 to 0.S%/DS.

"- - - The volume of suspended matters

-- indicates the best value at the range

1of 0.075 to 0.15%/S and the value

a -- .0 7=-:- deteriorates as the polymer volume

0 41 n ..j increases.

2000 P e 0.5 0 0.5

Polymer (%/DS) Polymer (%/DS)

101
d Line of conveyance

.e

0 0

-1 Pool depth

Line of conveyance

Figure 8. Illustration of effects of centrifugal force

of the screw conveyor is lowered, and cakes that are left behind affect the

property of processed water adversely in the form of increased turbidity.

When the difference of speed becomes greater than the level, churning by the

screw conveyor takes place to hamper separation by sedimentation and to give

adverse effects on the properties of cakes and processed water. Thus, it is

judged that the appropriate value of speed difference is 15 rpm.

Discharge

Changes in discharge have no conspicuous effects on the properties of

solid cakes and processed water. Usually, the properties of cakes and processed water deteriorate when the volume of discharge increases, but such a

tendency was not recognized in experiments at this time. It is considered

that the dehydrator can handle a greater volume of discharge than the test

volume.

Pool Depth

The deeper the pool becomes, the worse will be the dehydration of cakes

but the better the property of processed water. When the pool becomes deeper,

the residence time (treatment time) becomes longer to promote the settling of

particles and improve the quality of processed water. When the pool becomes

deeper, however, the barrage also becomes higher to limit the space of the

tapering part where the dehydration process takes place, resulting in poor

dehydration of solid cakes.

Pac Addition

Changes in the volume of PAC addition have no noticeable effects on the

quality of processed water, but its increase (300 ppm) favorably affects the

quality of solid cakes. In other words, the settlement of particles in the

upper clean liquid becomes sufficient at PAC 150 ppm.

Polymer Addition

The property of processed water shows the best value at about

0.15 percent of polymer and that of solid cakes improves as the volume of

polymer addition increases. It is considered that the effect of flocculating

102
agents (including PAC) on processed water in the decanter becomes the best at

the volume of that percentage.

EXAMPLE APPLICATIONS

Land Plant System

Outline of Project

a. Project name--- Barato River dredging project.

b. Work site--- Ishikari-machi, Ishikari-gun, Hokkaido.

c. Work period---September to November 1988.

d. The work consisted of the dredging organic sludge deposits in the

Ibara-to River using an oozing pump dredge and the

transport/discharge of the dredged slurry to an adjacent mud

discharge lagoon set up on land. Also established in the discharge

area are settling and filtering lagoons for treatment of separated

residual water. Dredged slurry is dried for about a half year by

natural drying until the start of the next year's work and then

loaded in dump trucks for transportation to final disposal areas.

Treatment by Mechanical Dehydration

A bifurcated pipeline was set up at the middle of the slurry pipeline of

the dredge to continuously take in the slurry (80 to 100 m3/hr) to a dehydration plant on land for treatment. Solid cakes and separated water were discharged into the lagoon. Solid cakes were also loaded on dump trucks directly

at the plant for transportation to final disposal areas. The arrangement of

the plant is shown in Figure 9. (See also Photos 1-3.)

A. Treatment capacity. Average results of treatment of the dredged

slurry, solid cakes, and separated water are shown in Table 8.

b. Characteristics. The annual average of dredging production in this

work is estimated at 80,000 m3 and that of the water content ratio in

original conditions at 300 percent. On these assumptions, the performance of the mechanical method was compared with that of the conventional method.

(1) Reduction of work area. The area required for a mud discharge

lagoon in the conventional method is 40,000 m3 . When the

mechanical method is adopted, the plant yard of 1,200 m3 is

enough for the treatment of the same amount of dredged slurry.

(2) Reduction of dredged slurry volume. After 6 months of natural

drying of the conventional method, the water content ratio of

the mud was 225 percent, representing a reduction in quantity

by 0.63 per cubic meter of original slurry. The mechanical

method scored a sand water content ratio of 25 percent and clay

(solid cake) water content ration of 130 percent. These

103
M ln e p

[--

Soda ash melting tankUi os

ThickeerP[ r generaok

I 13.

Figure 9. Plant arrangement

figures represent an average reduction of 0.37 per cubic meter of

original slurry.

(3) Continuity of work. Due to the length of time required for natural drying, disposal of sludge has to be done in the next year of

the dredging work. The mechanical method makes continuous work

possible, ranging from dredging to the final disposal.

(4) Reduction of sludge disposal volume. The volume of sludge disposal is estimated at 50,400 m3 for the conventional method and at

29,540 m3 for the mechanical method, both against the original

slurry of 80,000 in3 .

104
Photo 1. Land dehydration plant

Floating Plant System

Outline of Project

a. Project name--Tate River dredging project.

b. Work site--Tatekawa, Sumida-ku, Tokyo.

c. Work period--January 1989.

d. Contents of work. A 200-ps micropump dredge was used to dredge the

deposits of organic sludge. Dredged slurry was loaded on barges

which carried the load to the earth and sand disposal area inside the

central breakwater for final disposal.

Treatment by Mechanical Dehydration

A bifurcated pipeline was constructed in the middle of the slurry

(20 to 50 m3/hr) to the floating dehydration plant for treatment. Solid cakes

were loaded on the barge, and separated water was discharged into the river.

The arrangement of machinery and tools in the floating plant is shown in

Figure 10.

a. Treatment capacity. Average results of treatment of the dredged

slurry, solid cakes, and separated water are shown in Table 9.

b. Characteristics.

(1) Reduction of barges and frequency of transport. The work site,

located in the midst of a big city, was surrounded by densely

built-up areas close to the riverbanks, and the work space was

very limited, with river traffic hindered by a leg of a highway

105
Photo 2. Discharge of solid cake

106
Photo 3. Loading of solid cake on dump truck

TABLE 8. RESULTS OF TREATMENT UNDER

LAND PLANT SYSTEM

Item Treatment Result

Dredged slurry

Gravimetric concentration 1.9 - 11.0 wt%

Particle Size

Sand 1.0 %

Silt 94.4 %

Clay 4.6 %

Solid cake

Water content ratio 130 %

Discharged water

Suspended solids 25 mg/A

bridge standing in the middle of the river. Transportation of

dredged slurry was limited to water transport (by barges), and

many barges were required to handle the great quantities of

dredged slurry produced continuously. The floating dehydration

plant continuously separated the slurry into liquid and solid

parts, discharging the liquid into the river. Such a plant can

greatly reduce the volume of slurry for transport, thus cutting

the required number of barges.

(2) Increased efficiency and continuity of work. Traffic congestion on the river obstructed the operation of barges by

limiting the number of barges that could operate at one time.

Accordingly, the dredge was sometimes forced to stop its dredging operation. Dehydration treatment on a floating plant makes

possible continuous loading and transportation by a small number of barges.

107
Barge CL25..B6e.D2Sn)

(Storage 18m.Suo..5a-2S0d loading)

*"r - -. e,. _

I 0 .....

100A piping .

Thickener + Decanter -

N4 Collecor I*25s..7.UO2A. 3

I i -... : Unit house

c Vibrating filter

tower generator -12.450

'(rev water tank) 13m 40m4.i E : L~2OM .&?u. 1.90

Hydrated

20.0.

Figure 10. Floor plan of floating dehydration plant

undercarriage

TABLE 9. RESULTS OF TREATMENT UNDER

FLOATING LAND PLANT SYSTEM

Item Treatment Result

Dredged slurry

Gravimetric concentration 3.44 - 9.54 wt%

Particle Size

Sand 35.4 %

Silt 39.5 %

Clay 25.1 %

Solid cakes

Water content ratio 203 %

Discharged water

Suspended solids 39 mg/1

Floating Dehydration Plant

A full-fledged floating plant specializing in dehydration has been built

on the basis of experience and technology gained and developed from the use of

a simple floating plant consisting of a barge and portable equipment carried

on it. Possibilities of operation and movement along narrow rivers were taken

into consideration, and a new idea of assembling barges to build a floating

plant was adopted.

108
This floating dehydration plant is an assemblage of eight barges and has

been operating in the dic-dging project in a river (Ohyoko River) in Tokyo

since November 1989.

Specifications of this floating plant are shown in Table 10, and its

assembly diagram is indicated in Figure 11. (See also Photos 4-8.)

TABLE 10. SPECIFICATIONS OF FLOATING DEHYDRATION PLANT

* Size of a barge: W, 6 m x L, 12 m x D, 0.9-2 m x 8 barges

(Maximum draft, 1.5 m; maximuw height

above surface, 2 m)

* Size of ship after assembly of barges: W, 12 m X L, 48.5 m

* Production capacity: 200 m3/hr in slurry

Barge No. Major Equipment Loaded

I Crew cabin, about 25 m2 Toilet

Material warehouse, about 20 m2

Auxiliary 10-kVA power generator 1

2 Operation room about 11 m2 Fuel tank 7 m3

Main 750-kVA power generator 1 Inorganic flocculant

tank 10 m3

3-t ship operation winch 2 Hydrated lime tank 3 m3

A set of pumps 1

3 Centrifugal dehydrator 1 High polymer flocculant

tank 6 m 3 x 2

4 Various discharge conveyor 6

A set of pumps 1

5 Dust collector 2 Compressor

Vibrating filter, cyclone 1

Discharge conveyor I

A set of pumps 1

6 Raw water tank - 73 m3 Compressor

A set of pumps 1

7 Thickener - 70 m3

8 Slurry pump I

Others Densimeter 2 Flowmeter 5

Surface detector I pH meter 2 Level meter 13

Turlbidity meter 2 Monitoring TV 3

109
40 a 'h . . *

.414

-4 c

14c;L X 4

0 14

.Iu- ~ .4D* 

z $4

0o X 

L N£ 4II'

14110
Photo 4. Floating dehydration plant

Photo 5. Discharge of solid cake

i1
Photo 6. Loading of solid cake on barge

A!

Photo 7. Floating plant specializing in dehydration

112
Photo 8. Centralized operation monitoring room

CONCLUSION

There have been many occasions where the applicability of mechanical

dehydration to works of dredging sludge, earth, and sand was considered seriously. After all, however, attempts to adopt mechanical dehydration for

dredging have ended in small-scale experimental projects because of the

absence of appropriate dehydrators for dredging plus cost considerations.

Cases of mechanical dehydration treatment introduced in this report have

many characteristics which can solve many of the problems confronting sludge

dredge works. The floating dehydration plant introduced in one of the cases

of application is operating at present, and its performance and other features

are the subject of our long-term observation and research. On the basis of

data thus obtained, improvements will be made for more accurate management on

the execution of works, and efforts will be made for the establishment of more

reliable methods of dehydration.

113
INVESTIGATION ON RESUSPENSION OF RIVER SEDIMENTS

USING THE ANNULAR FLUME

DURING RAINFALL

AD-P0 0 6 459K.

i~i l11111\I\\\\I\IIII II\II Japan Sediments Management Association

2-7-12, Tsukiji, Chuo-ku, Tokyo 104, Japan

ABSTRACT

A long-range study on the hydrograph is necessary in estimating the pollution load from rivers

during rainfall. During the heavy rainfall, such a

load often corresponds to the total load at the ordinary flow level.

The present study is made to determine the volume of suspended matter during rainfall in an indoorscale circular waterway (2 m in diameter and centrally

driven). The stepwise increase in shearing stress and

migration of suspension from the river mouth sediment

was already reported using this device.

Further improvement is being made for an experiment under the condition close to heavy rainfall.

INTRODUCTION

The Japan Sediments Management Association was founded 15 years ago. In

the first half of these 15 years, our energies were concentrated on the establishment of "know how" regarding the treatment of harmful matters such as T-Hg

and PCB for which the tentative national elimination standard was established.

In the second half of this period, technologies in the past were reviewed to

investigate new fields relating to sediments, chiefly technologies to improve

environments such as organic sediments. At the same time, efforts were made

to examine the needs of this age including the waterfront, sea blue technologies, etc., and to draw the map of these technologies.

Our basic concepts of sediment purification will be described below.

First, the actual state of the vertical distribution of sediments, i.e., the

settlement of contaminants was investigated. Second, the elution rate

(mg/m2 /day) of contaminants from the sediments into water at the indoor level

during the contaminant accumulation process was studied, and a plan was made

for the sediment removal procedure or other countermeasures, taking into

consideration its influences on water quality, or in other words, the contribution to water purification. In recent years, the evaluation of the contribution to water quality purification, particularly in comparison with the

inflow load (external load), has often been requested. However, in practice,

it is difficult to evaluate such a load accurately. Therefore, it is

114 92-10779

92 4 24 2 1 3 III! 1lIii!Il ht11
necessary to develop a method to estimate the load at a simple indoor level.

For this reason, this subject is selected as one of the themes of our voluntary investigation.

OBJECTIVES OF THE INVESTIGATION

In some cases, to estimate the contamination load from a point source

and nonpoint source during rainfall, a hydrograph as shown in Figure 1 is

investigated. (See also Nikaido 1968.) This investigation should be carried

out for a long time, because waiting for rainfall will depend on the weather.

The key points of this estimation are clarification of (a) transport of

sediments and (b) the relationship between sediments and water quality. The

possibility of grasping these key points by using an annular flume of indoor

level was checked.

Figure 1 shows the relationship between shear stress of sediments in

harbors and the concentration of suspended matter. It was expected that if

intermittent measurement of the everchanging flow of the water was made to

assess the water quality, and if the same relationship between sediments and

rainfall intensity as noted in the river sediments could be proven onsite, the

approximate contamination load could be grasped easily. Figure 2 represents

an outline of the contamination load estimation method.

0

103

0

4-5

ro

So 10

0 7 DAYS wITH2JT NULCULA

,7 DAYS WITH NUCULA

2 A 14 DAYS WITH NUCULA

NUCULA: 1150/M z

0 2 I 6

Time (hours)

Figure 1. Relationship between rotation

time and suspended solids (SS)

concentration

115
Rainfall data arrangement and analysis Flow rate/SS load analysis

o Grasp of rainfall period o Examination of relationship

o Rainfall intensity occurrence between flow rate and SS load

frequency distribution o Preparation of estimation

" Examination of regional differences formula for SS load by flow

regionalrate

Flow rate data arrangement and analysis

o Examination of rainfall flowout

pattern

o Grasp of rainfall influence period

o Grasp of flow quantity increase

during rainfall

o Hydrograpn pattern classification

Calculation of SS load

" Grasp of load increase in rainy weather

" Grasp of flowout pattern in rainy weather -I

Flow-in contamination load

Figure 2. Contamination load estimation method

Incidentally, if the same can be applied to sediments, various problems

of sediments can be solved based on something like "sediment reference

points." This investigation was made according to such a concept. The

relevant literature and the intermediate results of this investigation are

described below.

EXPERIMENTS ON TRANSPORT OF SEDIMENT PARTICLES USING

ANNULAR FLUME

The results of this experiment may be used for the following items:

a. Estimation of suspended matter concentration and load during

rainfall.

b. Transportation of contamination deposits.

c. Estimation of settlement properties and resettlement of suspended

particles.

116
Experimental Equipment

Figure 3 shows the experimental equipment. Photos I and 2 illustrate

the setup in use. It consists of the annular flume which gives the superficial flow rate by means of the centrally driven shaft-type rotary flat plate.

The results of the long-term experiments conducted to estimate the amount of

suspended matter from sediments on the bottom of harbors using this equipment

were already reported. The dimensions of this experimental equipment were the

same as those of the equipment described by Tsai and Lick (1987).

I.Om

I15cc

.5c SEI EN , An 3c

Figure 3. Experimental equipment

Photo 1. Flume with the shear Photo 2. Overall view of experstress generating plate imental equipment

installed (for flow rate

measurement)

Sample

Samples were taken of sediments of rivers at the ordinary water level

and during rainfall, as well as contaminated sediments discharged from the

river into the lakes.

The resuspension of sediments will be greatly affected by the quantity

of flow and flow rate of the rivers as well as their physical and chemical

properties. Therefore, it is also important to select samples with different

117
properties for the investigation. Taking this fact into consideration, the

following four samples were used in this investigation.

a. The Ohhorigawa River (a river flowing into the Teganuma Lake).

b. The Teganuma Lake (after flowing in).

c. The Yunoko Lake (after flowing in).

d. The Tamagawa River.

As for sediments, its water content, particle size, specific gravity,

weight per unit volume, ignition loss, COD, T-N, T-P, etc., were measured. As

for the water quality, its turbidity, SS, COD (BOD), T-N, and T-P were determined. Figure 4 shows the composition of the particle size.

105Mm 2000m-m

SIEVE I I I I F I 7

4km 2S 1m 840.m 4760m

PARTICLE SIZE

90 PRODUCT CURVE

S 80-TEGA

0

E 70

10 o) OHHORIGAWA TAMAGAWA

-4-)

r_ 40

) 30

20 '

0 00 0.01

Particle size D (mm)

COLLOID~ C LY SL IESN CAS ADW

0.001 0.005 0.01 0.42 2.0 4.16

Figure 4. Composition of the particle size

Method

Invariable Overlying Water Depth

The annular flume was filled with superficial sediment (0 to 15 cm) that

settled on the river bottom to a depth of 2 to 3 m. Water was poured into the

annular flume to provide the depth of about 7 to 8 cm. After the rotary flat

plate was driven to give the superficial flow rate adequate time to make the

water muddy, the rotation was suspended for 24 hr to let the muddy water sand.

After it was confirmed that the suspended matter was stabilized as sediments,

the experiment was started.

118
The concentration of muddy water was adequately adjusted by conducting

the preliminary natural settlement test to provide mud to the thickness of

2 to 3 cm after settlement for I day.

Change in Overlying Water Depth

The water depth was adjusted to 2 cm, 5 cm, and 10 cm, and the flow rate

in the annular flume was kept constant.

Results

Properties of the Samples

Table 1 shows the properties of the samples used in this experiment.

Table 2 shows the water quality of the supernatant from which the mud was

separated in the natural settlement of muddy water.

The important parameters which govern the change from sediments into

suspensoid were the composition of particle size (shown in Figure 4) and specific gravity. Sediments of the Yunoko Lake consisted principally of silts

and clays, while sands mainly constitute those of the Tamagawa River. Sediment composition of the Teganuma River could be said to be between those of

the two described above.

Resuspension of

Particles at Same Water Depth

Tables 3 and 4 show the experimental results of resuspension of the particles of sediments at four places. The total rotation time of the rotary

flat plate was 0 to 235 min. Table 4 shows the flow rate in the annular flume

and the water quality of resuspended matter of the Ohhorigawa River, the

Teganuma Lake, the Yunoko Lake, and the Tamagawa River.

Figure 5 shows the relationship between rotation time and turbidity.

Relationships at Varied Water Depth

Tables 5a-5c show the relationship between the rotation time and turbidity until the flow rate become constant after changing the flow rate. Figure 6 shows those corresponding to respective relationships. The turbidity of

water varied greatly according to the water depth. The turbidity at the flow

rate of 0.2 m/sec and at the water depth of 2, 5, and 10 cm was 7,000

(150 minutes), 720 (20 minutes), and 200 (10 minutes), respectively. Their

ratio was 35:3.6:1. The turbidity of water cannot be simply compared with the

total amount of turbid water.

EXAMPLE OF CONTAMINATION LOAD ESTIMATION

Ordinary sediments of a river are the source of infinite contamination.

As an example, estimation of the load of the suspended particles from the

closed sewage conduit confluence system due to rainfall is described.

119
TABLE 1. BASIC PROPERTIES OF THE SAMPLES

Parameter Yunoko Ohhorigawa Teganuma Tamagawa

Water content (%) 782.6 92.6 239.7 24.5

Specific gravity 2.23 2.65 2.50 2.71

Weight per unit 1.08 1.51 1.35 1.29

volume (g/cm3)

Ignition loss (%) 13.7 19.9 17.4 1.69

COD (mg/g) 25.0 7.99 12.6 2.0

T-N (mg/g) 7.59 1.85 4.08 0.37

T-P (mg/g) 1.17 3.28 5.33 0.25

pH 6.9 5.4 6.5 6.4

TABLE 2. WATER QUALITY OF SUPERNATANT AFTER

SETTLEMENT OF MUDDY WATER

Parameter (mg/1) Yunoko Ohhorigawa Teganuma Tamagawa

Turbidity 16.5 41.0 51.0 450

SS 36.0 78.0 68.0 119

COD 6.6 7.3 11.2 12.2

BOD 2.4 2.1 6.6 5.7

T-N 7.17 3.92 3.90 4.35

T-P 0.08 0.30 0.89 0.54

120
aa0

'o 0a

a 8 

1! 0 C

R 98

C3'

CN; ~ C

II~ 'A121
TABLE 4. RELATIONSHIP BETWEEN FLOW RATE AND

WATER QUALITY

Ohhorigawa Teganuma

Parameter Blank 1* 2 3 Blank 4 5 6

Flow rate 0 0.033 0.107 0.20 0 0.033 0.107 0.20

(m/sec)

Time lapse 0 25 50 120 0 25 30 90

(min.)

pH 6.9 7.1 7.2 7.1 7.5 7.1 7.5 7.6

Turbidity 8.0 8.0 21.0 1,080 5.5 6.0 6.0 190

(mg/I)

SS (mg/I) 16.0 17.0 40.0 126 8.0 11.0 11.0 266

COD (mg/1) 5.3 5.6 4.8 103 5.3 6.2 5.7 25.6

BOD (mg/I) 1.8 2.5 1.7 8.5

T-N (mg/I) 3.15 3.33 3.77 9.71

T-P (mg/I) 0.22 0.20 0.23 10.4

Yunoko Tamagawa

Parameter Blank i 2 3 Blank 12 13

Flow rate 0 0.033 0.107 0.20 0 0.20 0.30

(m/sec)

Time lapse 0 25 90 120 0 10 40

(min)

pH 7.1 7.5 7.2 7.1 7.5 7.6 7.7

Turbidity 5.5 8.0 400 2,800 5.5 7.0 35.0

(mg/1)

SS (mg/I) 3.0 10.0 790 5,370 5.0 7.0 91.0

COD (mg/1) 4.5 5.4 82.0 545 7.8 8.2 12.6

BOD (mg/I) 1.2 2.8 13.5 72.5 1.8 2.3 4.5

T-N (mg/I) 5.71 5.95 15.2 66.3 1.69 1.73 3.03

T-P (mg/1) 0.05 0.05 1.06 1.56 0.48 0.50 0.72

* Run number.

122
I6

0.20 r/S

0 0.20.20 

rn/S

TURBIDITY

TURBIDITY (DEGREE)

(DEGREE) r Oi.o,4ORAWA

3. TEGANUMA

TECANUr

2

0.107 m/S

6

0.033 m/S 0.107 m/S

0.033 m/S

2 2

OVD17 0 -- 3 IN le- 2W MJ 212 - -) fl 7 ij ?j 2 ROTATION TIME (MIN) ROTATION TIME (MIN)

a. Ohhorigawa River b. Teganuma Lake

7

6-

.20 n/S 

4

0 30m/s

2 2- /S TURBIDITY

TURBIDITY (DEGREE).LAGAA

(DEGREE) ,o 0T G

7 6 L . 20,-/s

54 0. 107m/S

0 07/S

[ 0.033 m/S 2

i

ROTATION TIME (MIN) ROTATION TIME (MIN)

c. Yunoko Lake d, Tamagawa River

Figure 5. Relationship between flow rate and turbidity

123
TABLE 5a. MEASUREMENT RESULTS OF TURBIDITY IN SEDIMENTS

RESUSPENSION EXPERIMENT (WATER DEPTH: 2 CM)

Time Lapse (min.)

Flow Rate (m/sec) 0 1 3 5 10 20 70

0.033 4.5 100 100 100 100 - -

0.10 - 400 720 810 960 1,100 1,100

0.20 1,500 2,200 2,500 2,900 3,900 4,200

Time Lapse (min.)

Flow Rate (m/sec) 40 50 60 70 80 90 100

0.033 - - - - - - -

0.10 1,100 - - - - - -

0.20 4,500 4,800 5,000 5,200 5,600 5,800 6,200

Time Lapse (min.)

Flow Rate (m/sec) 120 150 180 210 240 270

0.033 - - - - - -

0.10

0.20 6,600 7,000 7,800 8,400 9,200 9,600

Note: Values are expressed in milligrams per liter.

124
TABLE 5b. MEASUREMENT RESULTS OF TURBIDITY SEDIMENTS

RESUSPENSION EXPERIMENT (WATER DEPTH: 5 CM)

Time Lapse (min.)

Flow Rate (m/sec) 0 1 3 5 10 20 30

0.033 8.0 17 16 16 16 - -

0.10 - 230 280 300 300 300 -

0.20 390 470 500 680 720 720

Note: Values are expressed in milligrams per liter.

TABLE 5c. MEASUREMENT RESULTS OF TURBIDITY IN SEDIMENTS

RESUSPENSION EXPERIMENT (WATER DEPTH: 10 CM)

Time Lapse (min.)

Flow Rate (m/sec) 0 1 _3 5 10

0.033 1.5 - - - 1.5

0.10 33 52 60 60

0.20 120 170 200 200

Note: Values are expressed in milligrams per liter.

The SS concentration due to rainfall was measured in the overflow from

the three closed sewage conduits and at the convergence point downstream (Figure 7). With the increase in the intensity of rainfall, the flow rate increased, but the SS concentration demonstrated a peak regardless of the flow.

If the overflow occurs when the rainfall intensity is 5 mm/hr or more,

the average rainfall intensity is about 8.4 mm/hr according to the frequency

diagram (Figure 8) of the rainfall intensity in this district, indicating

continuous rainfall for 75 hr. The water quantity corresponding to 8.4 mm/hr

is approximately 40 m3/sec. (This value is estimated from the relationship

between the water depth H and the rainfall intensity R , and the relationship between water depth H and the quantity of flow Q .)

125
TURBIDITY WATER DEPTH: 2C.4

(DEGREE) r

a. Water depth: 2 cm

ROTATION TIME (MIN)

TURBIDITY

b. Water depth: 5 cm (DEGREE) WATER DEPTH: 5CM

20 43 !Z' c

ROTATION TIME (MIN)

TURBIDITY c. Water depth: 10 cm (DEGREE)

ROTATION TIME (rIN)

Figure 6. Relationship between flow rate and turbidity at variable

water depth

126
1986 1/24 0

3 / RAINFALL INTENSITY

8/30 31-- ._ _ RAINFALL

SS INTENSITY (g/z) 200 20 (mm/h)

SS 8/11 ,

__ _ _ __ _ _ __ _ _ _IO

0 20 40 60 W 10 120 140 1E0 180

QUANTITY OF FLOW (m3/s)

Figure 7. Relationship between flow rate, SS, and

rainfall intensity at peak

h /1982 (TOKYO WEATHER STATION)

30 R-8.347

RAINFALL

PERIOD

20

10-

5 10 15 20 25 30 40

RAINFALL INTENSITY (mm/h)

Figure 8. Duration of rainfall in 1982 with intensity over 5 mm/hr

The contamination load W overflowed by rainfall under this condition

is calculated by the formula given below.

W = 40 m3/sec x 180 g/m3 x 3,600 x 75 hr

= 25.9 x 75 = 1,944 tons/year

If all the contamination load calculated is settled as the sediment, the

volume V becomes 5,542.3 m3 when calculated by the formula given below.

127
V = W + I X W = 2.5+ x 1, 944

= (2.451 + 0.4) x 1,944 = 5,542.3 m3

It will be necessary to determine the amount of sediment in the rivers

and the discharge place. Another subject for future study is the examination

method of the conditions to rationally determine the scale of facilities for

taking in the overflowed water (Figures 9 and 10).

12 10

FREQUENCy1 0 8.17 9

8

4.3 6 3.5 5_8 .

4 2.83 2 5 2 - 0.17, 0. , 1.0

0 - I ! I I

1 2 3 4 5 6 7 8 9 10 11 12 MONTH

Figure 9. Rainfall depth with intensity over 5 mm/hr

FREQUENCY 5

4

3

2- 24 HR CONTINUOUSLY

0 20 40 60 80 100%

Figure 10. Percentage and frequency of daily continuous

rainfall

In Figure 11, the settlement data obtained by the indoor test are plotted against the measured settlement rate during rajiufall. The settlement

distribution rate is estimated according to that of the similar river. Since

data on a large quantity of the rainfall intensity and the quantity of flow

128
CONTAMINANT IN THE OEILYAGAWA RIVER (APPROX. SS-200mg/l)

Z CONTAMINANT IN THE OHMIYAGAWA RIVER 100 (APPROX. SS 50mg/l) I i

( CONTAMINANT IN THE SHIMOJOGAWA RIVER IN

TOYAMA PREF.

NO. 4 DATA ON THE SETTLEMENT TEST OF SEDIMENTS IN A CERTAIN RIVER

PRODUCT 80 (MEAN OF 5 POINTS)

PERCE1TAGE

60

200

0 - -_- - - -H -- j__

0.01 0.03 0.1 0.3 1.0 3.0 6.0 10.0 30.0 100

PARTICLE SIZE COSETTLEMENT RATE (m/h)

P CONVERTED I S S O 20p S0;1 70, 00p 200;

BASED ON G2.1

Figure 11. Settlement rate distribution of the flow-in SS load

are generally provided, it is possible to make an estimate with reference to

these data.

The accuracy of such an estimation can be further improved, if the data

of the above-mentioned annular flume can be obtained.

CONCLUSION

The results obtained by the experiment using this bottom mud were

approximately similar to those on the sediments of the harbors (Figure 2).

Fig" re 5 shows the relationship between the composition of the particle

size and resuspension of the particles. As clearly seen in these figures, at

the rotational frequency of this experiment, along with the decrease in the

particle size, resuspension of the particles into the water increased. However, the increase could not be confirmed by experiment because of insufficient performance of the experimental equipment (the rotational frequency).

The speed at which resuspension of the limit in the sediments of the

Ohhorigawa River started was calculated from several formulae. As a result,

it was found that the flow limit rate, U* , was 19 to 46.8 cm/sec, and the

average flow rate of the river under this condition was 0.5 m/sec with the

maximum flow rate of 1.5 m/sec. Thus, it was concluded that since the flow

rate of the Ohhorigawa River in the present experiment was in the range of

0.107 to 0.2 m/sec, it was not fast enough to resuspend its sediments.

129
Items recommended for study in the future are:

a. The experimental equipment which can generate resuspension of sediments should be used.

b. The difference of the relationship with rainfall intensity between

the actual place and this experiment should be investigated.

REFERENCES

Nikaido, K. 1968. "Contamination Load in the Rivers During Rainfall," 14th

Sediments Purification Technical Seminar, November 1968, Japan Sediments Management Association.

Tsai, C.-H., and Lick, W. 1987. "Resuspension of Sediments from Long Island

Sound," Specialist Conference on Coastal and Estuarine Pollution, October 19-21, 1987, Kyushu University.

130
AD-PO06 460

HOPPER DREDGES APPLIED TO THE

ALASKA OIL SPILL, MARCH 1989

K. H. Patterson

Chief, Navigation Branch

US Army Engineer District, Portland

Portland, Oregon 97208-2946

J. F. Redlinger

Navigation and Plant Section

US Army Engineer Division, North Pacific

Portland, Oregon 97208-2870

ABSTRACT

On March 24, 1989, the oil tanker Exxon Valdez

ran aground in Prince William Sound, Alaska. This

accident resulted in the largest American oil spill

ever and spoiled one of the most pristine areas in

North America. In April 1989, the US Army Corps of

Engineers was requested to assist in the cleanup of

this disastrous oil spill. Two of the Corps' minimum

fleet hopper dredges, the Yaquina and the Essayons,

were dispatched to assist in collecting oil. Although

unmodified hopper dredges had never been used in this

capacity, the Yaquina and the Essayons proved to be

the most effective tools in the recovery of oil.

Given proper air support, adequate containment boom,

and commitment at the earliest possible time, hopper

dredges can make a significant contribution to the

cleanup of large oil spills.

BACKGROUND

A cataclysmic earthquake and tidal wave destroyed the port town of

Valdez, Alaska, on March 27, 1964. Measuring 8.6 on the Richter scale, it

remains the strongest earthquake ever recorded in North America. It created

an enormous tidal wave which engulfed Valdez and caused the death of at least

30 villagers. On the 25th anniversary of this tragic event, another flood

occurred; only this time the flood was man-made. At 15:04 a.m. on March 24,

1989, the oil tanker Exxon Valdez became impaled on Bligh Reef, hemorrhaging

oil into Prince William Sound at an estimated rate of nearly 1,000 gal/sec

(3,800 2/sec). Oil escaped from the ship with such force that it rose above

the water surface on surging 3-ft waves. Within 4 days, the oil slick covered

more than 100 square miles (260 sq km) of Prince William Sound, one of the

more pristine areas of North America.

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The Exxon Valdez has a capacity in excess of 1.4 million barrels of oil.

It is the newest and largest of Exxon's fleet of 19 ships and was delivered in

1986. When the vessel left the Valdez dock at about 9 p.m. on March 23, 1989,

bound for Long Beach, California, it was loaded with about 1.2 million barrels

of oil. The 987-ft Exxon Valdez was traveling at about 8 knots in the outbound channel when icebergs floating in the area were detected on the ship's

radar. The ship's captain requested and was granted permission to use the

inbound channel in order to avoid the icebergs. The ship, however, strayed

nearly 3 miles (5 km) beyond the eastern edge of the inbound lane. The Exxon

Valdez went aground on Bligh Reef about 25 miles (40 km) south of Valdez,

Alaska; ruptured 8 of its 13 cargo tanks; and lost an estimated 250,000

barrels of Alaskan crude oil. Thus, the stage was set for America's worst oil

spill disaster and the world's tenth largest recorded oil spill ever. The

world's largest oil spill occurred 10 years earlier, when nearly 2.2 million

barrels of oil from two tankers were spilled near Trinidad.

Alaskan crude oil is pumped from the United States' largest oil reserve.

The North Slope oil field is the source of nearly 25 percent of the Nation's

oil supply with an estimated yearly market value of more than $15 billion at

current prices. But in order to use the oil, a way had to be found to deliver

the oil from above the Arctic Circle to the refineries located in California

and in the Gulf and East Coast states. After much consideration, including

exhaustive environmental studies, a pipeline was recommended which would link

the North Slope oil field to Valdez, Alaska. Valdez is located in an area of

Prince William Sound which provides a deepwater port, open year-around. The

trans-Alaska pipeline owned by eight major oil companies is a 48-in.-diam,

789-mile (l,270-km)-long tube which carries about 1.5 million barrels of crude

oil per day from Prudhoe Bay on the North Slope to Valdez. In 1975, work

began on the pipeline which was the largest private construction job in American history. It involved laying and welding together nearly 102,000 sections

of 48-in. pipe. The pipe was laid under rivers and caribou migration routes

and over mountain ranges. It had to be refrigerated in places to avoid melting its permafrost coating. In other places, it was insulated against wind

chill factors of around -I00 ° F (-70 ° C). Within hours of reaching Valdez,

Alaska, the oil is loaded into one of more than 60 tankers that ferry it to

refineries on the West Coast or to Panama, where it is pumped through a Panama

Canal pipeline into other tankers that ferry it to Gulf and East Coast

refineries. By law, none of the oil can be exported. Since the pipeline

opened in 1977, an estimated 6.8 billion barrels of oil in more than

8,500 voyages have transited through Prince William Sound without incident.

But during the early hours on March 24, 1989, this commendable record came to

an end.

Bligh Reef is located toward the northern end of Prince William Sound.

Prince William Sound is a 2,500-square mile (6,500-sq km) wilderness that is

one of the most pristine and beautiful areas in North America. This remote

area contains a maze of inlets, mountains, and fjords and is protected from

the storms of the Gulf of Alaska by a series of islands. The Sound includes

about 2,700 miles (4,300 km) of shoreline--all wilderness except for a few

small villages including Valdez. The entire area supports a human population

of only about 10,000. Prince William Sound is home for hundreds of thousands

of birds, fish, and mammals, many of which were impacted by the oil spill.

The islands of the Sound provide nesting sites for birds such as kittiwake, a

gull-like bird, and puffin, a sort of diving duck about the size of a large

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grapefruit. The puffin has a distinctive orange and yellow beak. These

birds, which depend on the sea for their food source, arrive in the Sound each

spring to set up housekeeping on one of many islands that foster more than

100 nesting colonies. The Sound is also used as a resting and feeding area

for many species of shore birds, geese, and up to 5 million ducks, as they

make their way north to their nesting sites. Prince William Sound also supports the largest number of summering trumpeter swans in the world (about

1,000) and sustains from 5,000 to 14,000 tundra swans. The area is also home

to black and brown bears, as well as bald eagles, and is one of the most plentiful fishing grounds in North America. In an average year, the total salmon

catch is nearly 20 million pounds. Other fish catches total nearly 30 million

pounds, which include a half-million pounds of shellfish. In addition, a

$59 million halibut fishery is based in the Sound. Three species of whales,

including the humpback whale, migrate through the area each summer. Resident

marine mammals include more than 5,000 sea otters, porpoises, and killer

whales. Many of the islands within Prince William Sound are used as haul-out

areas where sea lions and harbor seals return each spring to bear their pups.

Crude oil generally has a density of about 0.85. When crude oil is

spilled in a saltwater environment, many changes take place. Experience indicates that within the first 3 days, those components that have a boiling point

under 2000 C volatilize. This change very much reduces the threat of explosion, making the oil relatively safe to collect, handle, and store. It must

be remembered, however, that the surface water of Prince William Sound is a

cold 3° C in the April-May time period. This temperature has a tendency to

slow down the evaporation process. As time goes on, however, the nature of

the material changes so as to make it very difficult to handle. About 48 hi

after the spill, depending on weather conditions and wave action, the oil

emulsifies with the seawater to form a very viscous material that contains up

to 70 percent water. It was our experience that this material had about the

same viscosity as refrigerated chocolate syrup. It was extremely sticky and

thus captured anything in contact with it, especially floating debris and

vegetation, including kelp. The color of this material turned to a light

brown and was referred to by many as "chocolate mousse."

This oily chocolate mousse severely impacted the beaches and shorelines

from Prince William Sound to Kodiak Island. It has been estimated that as

many as 700 miles (1,130 km) of beach and coastline were impacted by the oil

spill. In some cases after high tide, the oily goop left was as much as 6 in.

(15 m) thick. As the tides progressed through their normal routine, the oil

worked deeper and deeper into the coarse gravel/cobble beaches. It was reported that in some areas, the oil had soaked 4 ft into the beach, in effect

sterilizing the beaches of all life.

Many dead birds, otters, and other animals were washed up onto the

beaches. These were reportedly scavenged upon by the bears, eagles, and other

carnivores, thus impacting these animals also. By mid-April, the oil spill

had been blown southwest to the mouth of Cook Inlet and had caused damage to

the shoreline of the Katmai National Park on Shelikof Strait, across from

Kodiak Island. In so doing, the oil had been blown and carried by the current

a total of 500 miles (800 km) in about 3 weeks.

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MOBILIZATION

Both the dredge Yaquina and the dredge Essayons were outfitted on very

short notice. The vessels are designed with the capability to operate for a

period up to 30 days independent of any external support. In addition to a

30-day supply fuel and subsistence items for the crew, the vessels were loaded

with an oil containment boom, absorbent material, cleaning materials, extra

sleeping bags, heating coils, steam hoses, and steam wands. Also, considerable small parts for ship repairs, as well as parts needed to assist in loading and offloading oil, were placed onboard the dredges.

Some equipment necessary to the support of the oil cleanup operation was

rented, including an air compressor, 3-in. (7.62-cm) submersible and 3-in.

(7.62-cm) diaphragm pumps, and for each dredge a Marco Class I Skimmer. The

two types of pumps were placed onboard the dredge Yaquina to bring oil onboard

the dredge, or to assist in offloading oil from the dredge to a barge or other

containment facility. Neither of these pumps was successful due to the

viscous nature of the oil. The oil was too viscous to flow toward a normal

vacuum draw.

The boom brought from Portland was only 36 in. (0.9 m) in height and

proved to be too small to effectively collect oil under wave and wind conditions generated in these Alaskan waters. It is suggested that for future

operations, 72- to 84-in. (1.8- to 2.1-m) "sea curtain" booms be purchased and

stcckpiled.

Charts were furnished to both dredges for the anticipated areas where

the dredges would likely work. Due to the tremendous mobilization of equipment to Alaska for the oil spill, it was very difficult to acquire charts

locally. Charts additional to those supplied in Portland were subsequently

provided by the Coast Guard in Alaska.

In addition to the normal staffing onboard the dredges for dredging

operations, the crews were supplemented with two operators for the Marco

Class I Skimmer, a radio operator, and a public affairs specialist. The Portland District Safety Officer was initially onboard the dredge Yaquina. The

primary role of the Safety Officer was to ensure that appropriate tests were

conducted to determine the nature of the oil and to prevent any accidents

which might result from handling a "volatile" oil. However, as mentioned

before, by the time the dredges arrived in Alaska, the danger of explosion

from volatiles in the crude oil had passed.

A small survey vessel with crew was placed onboard the dredge Yaquina

with electronic positioning and fathometer capability. Depending on the area

where work is to be performed, it is likely that full hydrosurvey support

would not be required, although this capability does exist. An alternative to

normal hydrosurveys may be the side scan sonar, as discussed below. However,

the vessel did prove effective in assisting with maneuvering the oil containment booms.

A photographer was assigned to the dredge to document the conditions,

methods used, successes, and failures so that this information could be provided to others for a technical exchange of information.

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Once the dredges arrived in Alaska, additional supplies and equipment

were provided, including cots, folding beds, and sleeping bags for personnel

assigned both to Exxon and the fishing vessels working in the area. In

addition, considerable sorbent, foam pads, cleaning compound, paper coveralls,

and gloves were purchased. A 12-in. (30-cm) centrifugal pump with 12-in.

(30-cm) suction and discharge hose was delivered to the dredge Yaquina while

it was in Alaska. This pump was purchased with the intent of providing the

dredge capability for offloading oil. Due to the high viscosity and the considerable debris in the oil, this 12-in. (30-cm) centrifugal pump was ineffective. However, it was thought that if the oil could have been heated

adequately to reduce the viscosity, this pump would have provided the desired

offloading capability.

The dredges required special support for logistics and operations. A

team was sent from Portland District to Alaska to supplement the Alaska District Logistics and Operations staffs. Initially, this support consisted of a

military officer for onscene coordination between the dredges Yaquina and

Essayons and other vessels and agencies operating in the area, a project manager who coordinated between the Alaska Operations and Portland District Operations sections, and two logistics support personnel.

Transit time for response to an oil spill is dependent both on the

dredge and the weather conditions. The dredge Yaquina transited from Portland, Oregon, to Prince William Sound at an average speed of 9.5 knots. It

departed on 11 April 1989 and arrived at Prince William Sound on 17 April

1989. Because of adverse weather in the Gulf of Alaska, the dredge was forced

to travel on the inside passage route, which added approximately 1 day of

transit time.

The dredge Essayons is more capable of transiting in the face of adverse

weather conditions. The dredge departed San Francisco on 13 April 1989

en route to Astoria, Oregon, for outfitting. She departed Astoria, Oregon, on

17 April 1989 and arrived at her assigned station at Port Dick, west of

Prince William Sound, on 21 April 1989. She encountered favorable weather

conditions and transited at an average speed of 13.5 knots.

LOCATING AND COLLECTING OIL

When the dredge Yaquina and the dredge Essayons arrived, the oil had

been exposed to the atmosphere long enough for most of the volatile components

of the crude oil to have evaporated. Thus, the dredges were able to take on

the crude oil without risk of explosion. Since the Corps dredges are not

equipped for pumping inert gases into their holds, it will be again necessary

in the future to allow sufficient time for the volatiles to dissipate prior to

using the Corps dredges. The time needed is thought to be 24 to 48 hr.

The most efficient use of the dredges was in the recovery of large quantities of floating oil. Locating this oil, however, was a tremendous challenge. Full-time air reconnaissance was important to successful oil recovery.

With infrequent air support, it would often occur that oil collection equipment was in one location while the oil was several miles away. By the time

the oil collection equipment could be mobilized to the site of the oil, either

the oil had moved or very little daylight remained. Recommendations to solve

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the problem of both locating oil and getting equipment deployed to the proper

location include the following:

a. Assign sufficient aircraft, preferably helicopters, with deployable

flotation markers to each group of oil ;ollection equipment.

b. Develop a way to locate oil even at night and to project where oil

will be so that oil collection equipment can be directed to the

appropriate location.

c. Ensure that the dredges have communications capability to talk with

the various aircraft, including military aircraft and fishing vessels

operating in the area.

Once the oil is located and equipment mobilized to the site of the oil,

skimming operations can begin. A very important component of the skimming

process is the oil containment boom.

Initially a 36-in. (0.9-m) boom was used, but it did not prove satisfactory. The most effective oil containment booms were 72- to 84-in. (1.8- to

2.1-m) sea curtains.

A major limitation to using the boom with a dredge was that, in order to

be effective, the boom had to be towed very slowly. Maximum towing speed was

about 4 knots. At higher towing speeds the apex of the boom would submerge,

allowing the captured oil to escape. Also, at higher speeds, the need for

maintenance of the booms increased significantly.

Oil was successfully skimmed and collected in several ways. The most

common was to have two fishing boats pull an oil containment boom through the

water and capture any floating oil and associated debris. The collected oil

was so viscous that a bucket dropped onto it would not penetrate through but

would stay on top, or a shovel pushed into the oil could not be easily removed. Once the oil had been collected, the boom was pulled into a tight

circle. This circle was termed a "donut" and was rather effective in containing the oil until it could be loaded into a hopper dredge or barge. A dredge

would pull alongside the "donut" and pump the oil into its hoppers. Often the

dredges also deployed a boom attached to the dredge aft of the draghead, which

was a second line of defense to prevent the collection oil from escaping. At

times the dredge itself in co.bination with a smaller vessel was used to pull

a containment boom. Although it was not tried, there is no reason that containmet. booms could not be deployed on either side of the dredge in combination with other smaller vessels. In this way, the effective swath of oil

collected by the dredge could be doubled. Also, at times, "donuts" of oil

collected by fishing vessels were opened up directly in front of the dredge's

boom for the dredge to recollect. This method proved to be quite effective

because it increased the continuity of the overall operation.

LOADING OIL

Onloading of oil into the hoppers was very successfully accomplished by

using equipment already installed on the dredge. No extensive structural

modifications were required.

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The position of the dragheads on both the dredge Essayons and the dredge

Yaquina were changed by rotating the dragheads 180 deg. Under normal operations, the draghead is lowered into the water and pulled across the bottom,

sucking material up the dragpipe into the hopper much the same way as a household vacuum cleaner operates. Initially, the draghead was left in the dredging position and lowered into the collected oil. With the draghead in this

position, the dredge was ineffective in loading the oil into the hopper. If

the draghead was lowered too far into the water, only seawater was pumped; but

as the draghead was raised into the oil, the pump would lose prime. An efficient elevation or position of the draghead could not be found, partly because

of the constant vertical movement of the dredge. As an alternative, the draghead was removed, rotated 180 deg, and reattached to the dragarm. The draghead was then placed below the surface, underneath the "donuts" of oil. This

placement provided a huge suction mouth which allowed the oil to be sucked

through the dragpipe into the hoppers very quickly.

The pumping rate for the dredge Yaquina was approximately 100 barrels

per minute which included the oil, vegetation and other debris, and some seawater. The pumping rate for the dredge Essayons was about 350 barrels per

minute. The capacity for storage of oil onboard the dredge Yaquina is approximately 4,000 barrels, which compares to approximately 29,000 barrels on

the dredge Essayons.

During the loading operation with the draghead inverted, a critical factor was maintaining a suitable depth of the draghead beneath the water surface. The optimum depth was a function of the flow characteristics of the oil

and horsepower of the pumps. It was critical that the proper height for the

draghead be maintained so that the maximum possible percent oil could be

onloaded. If the draghead was located too far beneath the surface of the oil,

the percent of oil was quite low. If the draghead was too high, the pump

would lose prime.

It was apparent that significant improvements could be made in the

design of the draghead for oil recovery. The only modification to the dragheads used in the Alaska oil spill recovery was the construction of a cage

around the draghead to help prevent the oil boom and debris from being sucked

into the draghead. Furthermore, the suction head required for oil spill

recovery could be significantly different from the present design of the draghead. The following improvements should be directed toward helping increase

the percent of oil brought onto the vessel.

a.. Capability of minimizing water intake while maximizing the surface

area.

b. Smooth features.

C. A cage to prevent oil boom and debris from being drawn into the

dragarm.

d. A circular head which would allow drawing material from 360 deg.

e. An easily removable cleanout grate.

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Because some water is introduced during the onloading process, it was

necessary to decant the oil brought into the hopper. The oil separated

rapidly from the water, rising to the surface as it was lighter than seawater.

Decanting was accomplished by opening one of the hopper doors 2 to 3 in. The

water was thus slowly released until the desired oil level was reached; then

the doors were closed. Because of the debris present with the oil, there was

a problem with debris getting lodged in the door openings and preventing a

tight closure. Thus, it is recommended that before collecting oil, a screen

be fitted above each of the hopper door openings to remove any large debris

that would prevent the doors from closing.

OFFLOADING OIL

The three most limiting factors that affected efficiency in the collection and disposal of oil were the weather, difficulty in locating large quantities of floating oil, and difficulty in disposing of the oil once collected

in the dredges' hoppers. With no possible control over the weather, it was

often difficult to effectively locate and collect oil. It was during these

times and during darkness that collected oil was offloaded from the dredge

Yaquina to oil barges.

Once oil was successfully loaded into the dredge hopper, the problem

became how to offload it to a barge. Barges were provided to receive the oil

that had been collected. Because of the viscosity of the oil, which increased

the length of time it remained on the vessel, it was nearly impossible to

offload using conventional pumps. During the operation, many different pumps

were tried, all with limited success. The most successful pump was a

"Supervac," but its operation was painfully slow. The Supervac is a truckmounded vacuum system that is typically used to empty sewage tanks or similar

containments. It is essentially an air vacuum pump which has a long vacuum

line that can be moved to the oil surface. One of the problems was that the

oil was so viscous that suction simply created a hole in the oil and it would

not flow to fill the hole. Therefore, the vacuum line had to be moved from

point to point within the hopper, which was a very labor-intensive and

physically demanding task. One of the limiting factors of using the Supervac

was that the truck would fill quickly and then would have to be discharged.

This process was lengthy because the truck was designed to discharge through a

6-in. (15-cm) hose. The crew of the dredge Yaquina improved this discharge

rate by constructing a large rectangular box around the hatch of the barge.

Thus, the truck could open its back like a dump truck and discharge the oil

directly into the rectangular box. This idea was subsequently utilized by

contractors on other operations.

In an attempt to speed the offloading process, other options were also

tried. On the dredge Yaquina, a 12-in. (30-cm) centrifugal pump was installed. The suction line was attached to the hopper using a special flange

around a 12-in. (30-cm)-diam hole cut through the hopper bin wall. The flange

was located approximately 6 ft below che hopper bin deck level. During the

test, water was added to the hopper to keep the height of the oil at the discharge pipe level. Various heights were used, and the discharge valve was

adjusted to increase the vacuum. Four crew members with poles and large

knives on poles removed wood and assisted in breaking up the viscous oil. In

addition, a fire hose was used to create a slurry. At the time of the test,

the collected oil was approximately 4 ft thick. Although large quantities of

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water were pumped, a very small amount of the product was discharged, because

the oil would not flow to or into the discharge pipe, even with crew members

assisting. Because the oil was so viscous, the water below was pulled through

the oil and discharged. In addition, the impeller of the pump became heavily

plugged.

Another pump that was somewhat successful was the "Vac-u-vator." It

acted in a manner similar to the Supervac in that it was an air vacuum pump.

As explained above, the challenge of how to offload the oil was never

satisfactorily resolved, since it had an opportunity to decant and further

thicken to a point where it would hardly flow. This problem was compounded by

the intrusion of vegetation, wood debris, and other material that made the

mixture seem more like a sticky conglomerate than anything resembling crude

oil (which is relatively easy to transport by centrifugal pumps or several

other means). It will be necessary to fully research this challenge to ensure

that an effective offloading method is developed prior to engaging dredges

again on this type of operation.

One alternative that seems to show promise is to preheat the oil mixture

immediately before it enters a centrifugal pump. It is recommended that some

sort of heating system be developed that is steam driven. Electrical heaters

may pose potential safety hazards when generating temperatures in the range

required to liquefy the oil. There are several ways to implement such a system. The simplest might be to install a "Donkey Boiler" with the associated

steam coils and lines. Another is to build steam pipes in the hopper or have

them available as a quick add-on feature. One possibility would be to upgrade

the vessel's steam plant or to install an auxiliary plant.

Other methods such as augers or conveyers should also be given consideration during this much-needed research. Another alternative which would

totally eliminate the need to offload would be simply discharge the oil directly into a barge and not use the dredge hopper as an intermediate storage

area. It would be easy enough to either tow such a barge or have it pushed by

a tug. The challenge of how to decant the oil within the barge, however,

would have to be first resolved. On the surface, the task would seem to be

relatively easy in that the barge could be outfitted with pumps to remove the

water from near the bottom of the barge.

OTHER DREDGE USES

Once deployed to an oil spill recovery operation, the best use for a

dredge would normally be to collect and dispose of floating oil. In our experience in Alaska, however, the dredges were found to be able to act in other

capacities which increased the efficiency of the overall cleanup operations.

The spill response emphasized the capability of a dredge not only to handle

large volumes of oil-laden liquids, but to act as a self-contained command and

control vessel with full communications capabilities and thus as a mother ship

to fleets of smaller vessels (by supplying fuel, water, and other supplies).

Because of a dredge's ability to pump large volumes of water, consideration

was given to using a dredge as a pump station to provide water to shore to

flush the oil from the beaches. While a dredge could be used in this manner,

it was shown that such a deployment wou Id be relatively inefficient because

barge-mounted pumps could achieve the same result at considerably less cost.

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Also, in the final analysis, simply using water in an attempt to flush oil

from a beach is a futile effort and does little good once the initial layer of

oil debris has been removed.

CLEANUP

Cleanup of the vessels proved to be a formidable task. The dredge

Yaquina arrived in Seward, Alaska, for cleanup on 26 May 1989 and departed on

8 June 1989. Cleanup of the dredge was accomplished first by offloading the

remaining oil using Supervac. Then, a tremendous amount of labor was provided

by local contractors to thoroughly clean the vessel. Because of the viscous

nature of the oil, this task required a combination of steam with detergent

and hand labor to wipe down nearly all surfaces on the dredge.

The dredge Essayons arrived in Seward, Alaska, for cleanup on I June

1989. She departed Seward 47 days later on 18 July 1989. Cleanup of the

dredge involved the same initial offloading procedures for oil in the hopper.

In addition, however, it required intensive manpower operations for offloading

the 180 cu yd (125 cu m) of oil-contaminated sand, gravel, and kelp. One of

the most costly lessons learned during this operation was the result of placing sand, gravel, and other oil-contaminated material into the hopper of the

dredge. The emulsified oil, sand, and gravel mixture turned into asphaltic

concrete and had to be hand-chipped and sandblasted from the hoppers. This

material was onloaded during operations at Katmai National Monument. The

rotting organic material resulted in a highly obnoxious odor which required

respirators for those working in the hopper area. Also, there was the problem

of sealing the hopper doors. These doors are not designed to be watertight,

and water continued to leak, hampering efforts to clean the lower portion of

the hopper. This problem was finally resolved by using divers to seal the

doors from below. The water in the hopper could then be pumped out and the

remaining material removed. Because of the challenges which this operation

provided, cleanup of the dredge dragged on. Although the dredge Essayons is a

much larger vessel than the dredge Yaquina, it is felt that cleanup of the

dredge Essayons could have been handled in a time frame comparable to that of

the dredge Yaquina if oil-contaminated sand, gravel, and vegetation had not

been placed in the hoppers.

The dredge Yaquina returned to its home base in Portland, Oregon, on

15 June 1989. The dredge Essayons arrived on 21 July 1989.

RECOMMENDATIONS AND LESSONS LEARNED

Preparedness

It is clear to everyone that worked on the oil spill that a timely

response is absolutely critical. This absolute need for an immediate response

is a compelling reason to have a standby capability to collect and remove

large quantities of spilled oil in a short amount of time. Even if those

responsible had been able to totally boom off the area in the immediate vicinity of Bligh Reef, it is doubtful that the boom could have maintained its

integrity during the wind storm of 26 March 1989. Those 60-knot (llO-km/hr)

winds would have most likely destroyed any attempt to corral and contain a

spill of this magnitude. It is imperative that a system be devised to allow

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for quick recovery of oil from the water. Any spill that takes place in open

water will be extremely difficult to contain for a sustained period of time.

Dredges are deployed around the world and are concentrated near areas of

high industrialization, i.e., areas of high risk for some kind of oil spill

disaster. Because of their mobility and intrinsic ability to pump large quantities of oil, dredges could easily be used to complement the oil industry's

own resources in fighting large oil spills.

Methodology

During an oil spill recovery operation it is important that a dredge be

primarily used for its highest and best use which, in our opinion, is to

remove oil from the water surface. In Alaska, much of the vessel's time was

spent mobilizing from one hot spot to the next. During this travel time the

dredge was unproductive. In an effort to increase productivity, a floating

boom was attached to the dredge so that oil could be collected as the dredge

moved from position to position. The boom, however, reduced our speed to less

than 4 knots. Greater speeds caused the boom to submerge and lose part or all

of the collected oil. Thus, a dredge should work with a series of smaller

collector vessels. In this way, the dredge could spend most of its time recovering oil and leave the job of collecting oil to smaller, less costly vessels. A type of flotilla was envisioned under the command and supervision of

a Flotilla Manager, located aboard the dredge. A hopper dredge would be the

hub of the flotilla responsible for gathering, collecting, and disposing of

all floating oil within a distinct geographical area. Each flotilla would

consist of a dredge, recovery and collector booms, the necessary vessels to

tow the booms, reconnaissance aircraft, and other miscellaneous equipment to

support the oil recovery effort. A geographic area of responsibility would be

assigned to each flotilla. Within this area, floating oil would be gathered

by small collector booms, transferred to larger storage booms, and then pumped

into a hopper dredge for final disposition to an oil barge. It is expected

that each flotilla would be generally self-sufficient and thus require little

support from other sources. Air support to locate recoverable oil and communications to coordinate activities are absolutely essential ingredients to the

flotilla.

A typical operation for such a flotilla would include the following

considerations:

a. Each flotilla would be assigned and responsible for a specific geographical area. The size of the area would be dependent on many

factors, including:

(1) Type and length of coastline.

(2) Quantity and extent of oil.

(3) Weather conditions.

(4) Resources available (such as amount of boom).

b. The area would be further subdivided. Two vessels with collector

booms would be assigned to work in the smaller areas in and out of

141
bays and close to shorelines. It is therefore essential that these

units be relatively small and maneuverable.

c. Storage units with larger towing vessels would service up to 10 collector units and would transit between locations to pick up oil from

them as well as collect oil themselves in the open water.

d. The dredge would sail between storage booms, pump out the oil, and

then move to the next storage unit location. A large oil barge with

a pump would be moored within the area to allow offloading of the

dredge when it reaches capacity or during night hours when skimming

becomes inefficient.

The dredge would be offloaded regularly, prior to such time the oil

could "gel."

Solids from beach cleanup should be loaded directly onto barges, rather

than into the dredge hopper. Barges are much less costly and can maneuver

closer to the beach.

Where possible, a conveyer belt system for loading solids from the beach

cleanup to a barge is suggested. Bags of debris could be broken directly onto

the conveyer for direct loading onto the barge.

Coimunications

There is a definite need for satellite communications, which would include a FAX machine onboard both dredges. This equipment would enhance the

ability to act as a command and control vessel. It would also enhance administrative matters, such as submission of reports, requisitions for supply, and

public affairs releases to the media.

Another communication concern is the availability of handheld radios for

both the crew on the dredges and the crew on the fishing vessels. Such handheld radios should be designed for rugged ocean environment conditions.

Reporting requirements for production during oil cleanup operations are

very demanding. Because of the nature of oil cleanup operations, it must be

pointed out that both hopper measurement and barrel count is judgmental at

best. The oil and water mixture which is loaded into the hoppers initially

separates fairly quickly. However, it does not totally separate. There are

still pockets of water in the oil. In addition, neither the viscosity of the

oil nor the thickness of the oil on the surface of the water is uniform. Over

time, water and oil do continue to separate. Thus, the oil in the hopper does

become more dense and thus smaller in volume. Because of the changing nature

of the oil, it is important that all agree on how the information should best

be gathered and understand that volumes reported are only estimates.

Equipment

The 72- to 84-in. (1.8- to 2.1-m) sea curtain oil boom proved to be very

effective. There was, however, a severe lack of this type of boom. It is

recommended that each of the dredges used for oil recovery have available a

142
complete kit of this boom of approximately 1,000 ft (300 m). The kit should

include storage drum and repair parts.

It is also recommended that net reels on fishing vessels should be investigated to determine if they could be adapted for boom deployment and retrieval. Storage of the boom on the reels would be ideal.

Since this cleanup was the first time that the dredges had been deployed

in conjunction with oil booms, there were no adequate tie-off points. It is

recommended that a bracing system be constructed that would allow the bridle

rope either to be tied off near the water line or to go through a fair lead

and be tied off on deck.

A continuing problem when loading oil from the donuts was that the oil

boom would tend to be sucked into the draghead and often damaged. As a

result, a conical cage was made of steel bars for the dredge Essayons. The

tops of all the bars should come together about 3 ft above the draghead. It

is recommended that round stock or heavy pipe be used as opposed to flat or

angle stock. This cage would also prevent large debris from clogging the

draghead and forcing a shutdown. In addition, to address the problem of debris, it is advisable to have 20-ft (6-m) pike poles onboard for use in

clearing the debris from the vicinity of the draghead. The sharp point on a

typical pike pole should be rounded because otherwise it can easily cause

damage to an inflatable boom.

There is a clear need for a small boat with an outboard motor, such as a

Zodiak. A small skiff was useful for assisting in oil boom deployment and

also allowed the crew to go to shore to transfer people and equipment. During

oil recovery operations in Alaska, helicopters frequently brought people and

equipment onto remote beaches. Without such a small vessel, transportation

from the beaches to the dredges would be very difficult.

It was apparent that there was a need for additional information on

depths and locations of hazards to navigation. The shoreline in Alaska is

extremely hazardous and has many uncharted areas. Use of a side scan sonar

should be investigated to determined if such equipment could detect hazards

before they become a problem to the ship.

During the cleanout of the dredge Essayons in Seward, it become apparent

that inability to completely seal the hopper doors was a problem. Although

not a problem during normal dredging operations, it became very difficult to

remove all contaminated debris from the hoppers because of water leakage

through the hopper door deals. It is therefore recommended that an inflatable

tube the length of the hopper doors be developed that would allow quick sealing when necessary.

The following recommendations for equipment could apply equally to both

the dredge Yaquina and the dredge Essayons. Other pieces of equipment which

should be placed onboard a dredge prior to deployment for an oil cleanup operation include:

a. A Coast Guard-approved gasoline storage area aboard the dredge for

gasoline storage. The gasoline would be used to resupply skimmers

and small craft outboard engines.

143
b. A sonic ullage gauge for accurate sounding of oil. This device could

be similar to systems used on tankers with an additional sonic gauge

to determine the actual oil/water layer in the hopper.

g. Cages around the screws of the workboats to protect the screws from

debris in the water and rocks when going ashore for passenger pickup.

CONCLUSION

Based on their excellent performance in the Alaska oil spill cleanup,

the hopper dredges have a very useful role in any future large oil spill

recovery efforts. Provided with the proper air support and equipment, and

provided they are deployed at the earliest possible time, hopper dredges

remain a strong, effective option for meeting oil spill cleanup requirements.

ACKNOWLEDGMENTS

The authors would like to acknowledge the crews of both the dredge

Yaquina and the dredge Essayons for their assistance in preparing this paper

as well as their extraordinary efforts in dealing with the oil spill. It was

only through these efforts that a workable plan was found that proved the

effectiveness of dredges in oil spill recovery operations. We would especially like to acknowledge the following for their written comments on this

paper:

Kevin Brice, Major, US Army Corps of Engineers

Charles Heaton, Captain, US Army Corps of Engineers

Theodore Hunt, Master, Dredge Yaquina

Miguel Jimenez, Master, Dredge Yaquina

Neal Nyberg, Chief Mate, Dredge Yaquina

James Holcroft, Chief Mate, Dredge Yaquina

Robert Hopman, North Pacific Division, Corps of Engineers

Jennifer Jones, North Pacific Division, Corps of Engineers

Guy McConnel, Alaska District, Corps of Engineers

144
AD-P006 461

INFLUENCE OF ANOXIC WATER IN TOKYO BAY AND ITS

311111111111111111MANAGEMENT PLANNING

J. Iwakami, H. Fuse, and H. Matsui

Ministry of Transport

Takasima 1-2-5, Nishi-ku, Yokohama 220, Japan

ABSTRACT

Recently, upwelling of anoxic water, called

"Aoshio," has been frequently found in the inner part

of Tokyo Bay. As the occurrence of Aoshio causes

shellfish to perish, the study of Aoshio is very important to maintain the natural environment.

In this paper, the analysis of Aoshio on basis

of past data and field studies in 1987 is presented

with a simulation model for Aoshio occurrence.

Principal results are as follows:

A. The occurrences of Aoshio are most

frequently found from July to September and near the cost of

Funabashi.

b. The mechanism of Aoshio occurrences

is mainly due to coastal upwelling

effect of anoxic water mass near

bottom through northern wind duration in summer.

c. Simulation model studies for Aoshio

have modeled the actual phenomenon

in the field, such as in 1987.

d. Dredging and capping are the most

effective ways to diminish Aoshio

occurrence.

INTRODUCTION

The water quality in Tokyo Bay has remained on the same level since 1975

under chemical oxygen demand (COD). Although when considering values of COD

it is seen that the water quality is not contaminated, the water in Tokyo Bay

actually reaches high eutrophication in another viewpoint such as frequencies

of red tide in summer.

145 92-10781

92 4 24 215 ifl fll
Recently, the so-called Aoshio occurs frequently in summer along the

coast from Urayasu to Chiba. Aoshio may be the phenomenon by which the anoxic

water mass near bottom is upwelled. This phenomenon causes severe damage to

the fishery and sometimes kills shellfish.

As one part of several studies to improve water quality, studies for the

management plan of Aoshio have been carried out in the interior of Tokyo Bay

from 1986 to 1988 under the Second District Port Construction Bureau, Ministry

of Transport.

In 1986, the data about red tide and Aoshio were collected and synthesized. In 1987, the field observations were performed. In these studies,

efforts were made to elucidate the actual cause of Aoshio and the mechanism

for its occurrence.

Besides, in 1988, the simulation model for an Aoshio occurrence was constructed, and the accuracy of this model and the man-gement plan for protection of Aoshio were discussed.

OCCURRENCE OF AOSHIO

Aoshio corresponds to the phenomenon which shows widely blue and white

color on the sea surface for several days. The expression, Aoshio, is simply

a popular name and is not defined quantatively.

The color of seawater in the inner parts of Tokyo Bay is usually yellow

green or brown in summer, but at the occurrence of Aoshio it changes to blue

white or blue green. In general, these changes of color help locate the occurrence of Aoshio. At the same time the transparency of seawater increases

to at least 1 meter and is often several meters higher than it is in the ordinary water without Aoshio. Other characteristics of Aoshio water are that the

temperature and oxygen are lower, and the salinity is higher than offshore.

According to past data, Aoshio was first found in 1951, but from 1965 to

the 1970's it occurred very often. In fact, occurrences of Aoshio tended to

be found more frequently in the 1970's.

Considering seasonal variations of Aoshio, it seems to occur generally

from May to September, especially from July to September. The sites of Aoshio

are concentrated near the coast of Funabashi, as discussed later. The occurrence of Aoshio in the past was described by Kataoka, Fuse, and

Komatsu (1988).

MECHANISM OF AOSHIO OCCURRENCE

From the studies carried out on the basis of past data in 1986, the

mechanism of Aoshio occurrence was supposed to be as follows.

Considering the trend of oceanographical conditions of Tokyo Bay in summer, vertical distributions of water temperature have remarkable thermocline,

and surface salinity is very low due to discharge of fresh water.

According to these factors, the water mass in Tokyo Bay indicates remarkable stratified structure in summer, and then vertical convection of water

146
is naturally controlled. Accompanying the lowering of vertical convection,

the anoxic water mass may be formed near bottom, especially in the inner part

of Tokyo Bay. If the northern wind blows continuously there, the surface

water near the coast moves offshore, and the compensation for this water will

be done by the bottom water near coast in the interior of Tokyo Bay. Thus,

the appearance of the anoxic water mass near the surface generates the Aoshio

(Figure 1). As noted, the cause of the characteristic blue-white color of

Aoshio is due to the formation of sulphur by the contacts between the sulphuric ion of the anoxic water mass and dissolved oxygen near the surface

(Samukawa et al. 1987).

4 northern wind drift

density offshore current generation e"A eShiO"

rXj. . stratification compensation current

anoxic water mass contaminated organic mud

Figure 1. Supposed schematic map for mechanism of Aoshio

occurrence

FIELD STUDIES OF AOSHIO

Process of Research

In 1986, it was presumed that Aoshio should have occurred from coastal

upwelling of the anoxic water mass formed under stratified density structure

conditions and in a period of continuous blows of the northern wind in summer.

Another factor to consider is the effect of gentle slope in bottom topography.

Thus, in 1987 in order to investigate this effect of bottom topography,

the field studies were carried out for limited sites of frequent Aoshio

occurrences.

Figure 2 and Table 1 show conditions of the Aoshio occurrence and the

area of Aoshio on the basis of field operation in 1987, respectively. The

observations were performed concentrating on 18 days from August 11 to September 15 because August and September are recognized to be the frequent period

for Aoshio occurrences.

Aoshio occurrences were observed for 10 of the 18 days (Table 1). The

study area was restricted offshore of Funabashi channel because of information

from past data. In this area, Aoshio occurrences were frequent between the

area north of Funabashi channel and the shoreline from Funabashi to Makuhari

(Figure 2).

147
Ichikawai lchkaa B Funabashi

t7 Sodegaura

Urayasu .0 Seg

.4L %lakuhari

Dredge hole * Dredge hole

.4 N .2

93 Funabashi channel

Figure 2. General map of area where Aoshio

occurred (shown in shadow)

TABLE 1. AOSHIO OCCURRENCE IN THE INNER PART OF TOKYO BAY*

Area

Date and Time Site of Aoshio Occurrence ha

Aug. 25 (13:00-12:00) Mooring station of Funabashi 22

Aug. 26 (9:10-12:30) North of Ichikawa channel 29

Aug. 27 (approx. 15:00) North of Funabashi channel 122

Sep. 2 (12:50-16:20) Offshore Takasu 11

Sep. 4 (9:30-10:30) Offshore Sodegaura and south 44

of Ichikawa channel 114

(12:50-17:00) Offshore Sodegaura 25

Along Ichikawa channel 64

South of Ichikawa channel 58

Offshore Makuhari 47

Sep. 5 (9:10-13:00) North of Funabashi channel 158

Sep. 6 (8:20-11:20) North of Ichikawa channel

and interior 164

Sep. 12 (8:50-13:10) North of Funabashi channel

and mooring station 110

(13:30-16:30) Offshore Makuhari 223

Sep. 13 (7:50-12:10) Mooring station of Funabashi 110

(13:10-16:30) Mooring station of Funabashi 83

and offshore Makuhari 115

Sep. 14 (8:40-12:10) Mooring station of Funabashi 153

and offshore Makuhari 243

(13:00-17:00) Mooring station of Funabashi 170

• Period of observation: August 11-September 14, 1987.

148
The Aoshio scales, with regard to duration and area, were considerably

large during the periods September 4-6 and September 12-14. With the exception of the above-mentioned Aoshio in 1987, other Aoshio occurrences were

reported on June 29 (near Ichikawa channel), July 22 (near Ichikawa channel),

and August 2 (at Chiba port and near Funabashi channel) (Chiba Prefectural

Fisheries Experimental Station 1987).

Wind Conditions at Aoshio Occurrence

Since it is said that Aoshio appears depending on the northern wind duration in summer, observation results of wind on the sea surface were analyzed

in summer 1981 to verify the relationship between Aoshio and wind (Figure 3).

The continuous blows of northern wind were found from August 25 to 26,

on September 2, from September 4 to 6, and from September 12 to 14 or on the

preceding day of these intervals. These periods correspond to the occurrence

of Aoshio (Figure 3).

Although the same northern wind durations were found on August 11 and

18, Aoshio did not occur. Since according to oceanographical data in the

inner part of Tokyo Bay the anoxic water masses had not been found on the days

previously mentioned, the possibility of an Aoshio occurrence was very low.

From Figure 3, the north and northwest winds were dominant from September 4 to 6, and the north and northeast winds were dominant from September 12

to 14. The former brought Aoshio west of Funabashi channel, and the latter

east of it, respectively. Thus, the correlation between the site of Aoshio

and the wind direction indicates that the wind might induce Aoshio.

Oceanographical Conditions at Aoshio

The time series of vertical distributions of water temperature,

salinity, and oxygen are shown for station 9 north to Funabashi channel in

Figure 4. (See Figure 2 for locations of these sites.)

The reason that Aoshio did not occur on August 11 and 18 when northern

winds were blowing on both days might be dependent on oceanographical structure. Namely, the temperature and salinity were almost same from surface to

bottom. Besides, values of dissolved oxygen (DO) were indicated above 4 mg/1

through all depths. Since salinity in all layers was 28 to 30 ppt on

August 11, 14, and 18, salinity values near the bottom were lower than normal

conditions. From these data, it is supposed that the anoxic water masses

disappeared or were removed offshore by a strong vertical disturbance due to

duration of southern wind from August 4 to 10 (Figure 3). The same phenomena

with uniform temperature and low salinity at all depths were found on

August 28 and September 1, 8, and 12. On the other hand, water temperatures

in all layers were low but the salinity near the bottom was high, namely,

above 32 ppt; the values of oxygen were below 4 mg/i at the Aoshio occurrence

from September 4 to 6 and -rnm September 12 to 14.

Water qualities were compared before and during the Aoshio occurrence.

During the Aoshio occurrence water temperature and oxygen were lower, and

salinity was higher on the surface and near bottom than before the occurrence

(Kataoka, Fuse, and Komatsu 1988).

149
(1) Aug. 1987

W~W E

Isiis

(2) Sept. 1987

09/(D2O30405QbO7UO9 101 1i2 U 4 15 b 1 716 9 -

2 1 222324252L -28293ID/Ol

Note: 1. Underlined dates are observation days.

2. Arrows show ~oshio occurrence.

Figure 3. Continual wind vectors for 24 hr at Keivo Sea-Berth

150
W 8 14 is 21 252828 /1 2 4 5 S 8 10 12 13 14

2.5, water temp

depth

7.5

(a) 8/11 14 18 21 2526 28 /1/ 2 4 5 8 8 10 12 13 14

25(2) Salinity

depth f3

7.5 " 1

(3) DO concentrationkX h

(-) 8/11 14 18 21 2528 28 SI? 4 5 8 8 10 121314

2. 5

depth ~i

depth -1--.-0o

7. 5

Figure 4. Time series of vertical distributions of water

temperature, salinity, and dissolved oxygen

(August 11 to September 14, 1987)

Distributi(ns of Anoxic Water Mass

In summer when stratified layers develop, DO values in the bottom tend

to be low in all interior locations of Tokyo Bay (Tokyo Metropolis, Chiba and

Kanagawa Prefectures 1988). Thus, if the coastal upwelling originated by the

northern wind occurs, it is possible to cause an Aoshio to occur anywhere in

the inner part of Tokyo Bay.

Another supposition about an Aoshio occurrence that should be considered

is its relation to bottom topography. The dredge holes remain in several

places after the reclamation work. It is supposed that these holes fulfill

151

0 | 
the stagnant role for water movement. In order to assess whether these dredge

holes have an important function for anoxic water mass formation near bottom,

DO values were measured near bottom (I meter above the bottom) in the inner

part of Tokyo Bay in 1987. The appearances of anoxic water (below 2 mg/1) are

shown in Figure 5. In this figure the frequencies of anoxic water were given

by numerals that appeared among all observations. Although anoxic water

masses were found in all observations of the dredge hole, they were also found

in about 75% of the non-dredge hole areas. According to these data, the principal cause of an Aoshio occurrence in the inner part of Tokyo Bay should not

be due to the local topographic effect such as the dredge hole but should

depend upon results showing wide distribution of anoxic water by meteorological and oceanographical conditions.

Ichikawa Funabashi N Ichikawa Funabashi N

*SodegauraN Sodegaura

Urayasu Uravasu

Dredge hole ur~ h,~ ole Ta/ uDredge hole 8! .13 redge hole Taa/ % Ma14r '' 3 1 I

1.3 h : . 1.5 e3 .13

'~s Funabashi channel o 2I.~ .12 Fnabashi channel n

Figure 5. Conditions of appearance of anoxic water mass

(August 11 to September 14, 1987)

FORECASTING MODEL FOR AOSHIO

Fundamental Consideration of This Model

The occurrence process of Aoshio in Tokyo Bay is summarized as two

processes:

a. Formation of anoxic water mass near bottom in the stratified period

(biological and chemical process).

b. Upwelling of anoxic water mass accompanying the duration of the northern wind (physical process).

To construct the forecasting model for an Aoshio occurrence, it is necessary to express exactly what is demanded of both processes in the model. In

the biological and chemical process, it needs to express the consumptions of

oxygen near bottom through phytoplankton production and its decomposition of

bottom mud. In t.-ie physical process, it is necessary to indicate the physical

structure of the coastal upwelling about the anoxic water mass near bottom

through wind drift on the surface.

Since the duration of Aoshio is for 2 or 3 days (maximum) and the states

of anoxic water are continued even near the surface, it must be considered to

consume oxygen by the oxidation of sulphuric substances in anoxic water

152
(Samukawa et al. 1987). By these examinations it is suggested that the behavior of sulphuric substances is a very important factor in the construction of

the model of Aoshio.

When modeling the two previously discussed processes, it is important to

fulfill the following conditions:

a. Expression of nutrient cycle structure within the low trophic level.

b. Expression of processes of sulphide behavior and oxygen consumption.

c. Expression of wind drift current and density current.

d. Expression of three-dimensional model which is capable of indicating

the behavior of the anoxic water mass near bottom.

In this study, a four-layer model is used as transport movement

phenomena including wind drift current and density current; the model of nutrient cycle is shown by links of trophic chain in the low trophic level.

These processes in both models can conveniently be calculated in two

steps:

Step 1: Forecast the formation of an anoxic water mass

(transport movement without wind).

Step 2: Forecast the upwelling of an anoxic water mass

(transport movement with northern wind)

The four-layer model of transport movement is shown in Figure 6 including tidal current, constant flow (residual current, density current, and wind

drift current), and diffusion process of density. To calculate water quality,

the inodel of nutrient cycle developed by the Port and Harbour Research Institute includes organic phosphorus, inorganic phosphorus, DO, and COD as indicated (Horie 1987). Here the behavior of sulphide is added to improve this

model for better simulation of Aoshio.

In this model, layers are divided into four layers: 0- to 2-m depth,

2- to 5-m depth, 5- to 10-m depth, and below 10-m depth.

Definition of Aoshio in the Model

The state of anoxic water on the sea surface is treated as an index of

Aoshio in this model. According to observations in 1987, the areas of Aoshio

occurrence almost correspond to regions with DO concentration below 2.0 mg/1.

The critical DO value of benthos survival, especially shellfish, is about

1.5 to 3.0 mg/1. Therefore, the definition of anoxic water mass is expressed

by DO concentrations below 2 mg/1.

153
IchikawaIchikawa4 :<

1 Uraa(s 2 )Uraya'su '

Ichiara chihara

Sh inagawa hngw

isarau Kisarazu

YooaaYokohm i

mean oncenratio 7 0mean concentrat ion

meang concentr aio during one tidal -

during one tidal period ( /, .

Funabashi Funabashi

Ichikaw'a Ichikawa

(lUraya t 4 ray as

chihara (DO cn r iochihara

154

KisarazuKisarazu

mean concentration mean concentration

period (mg/l) period (rag/l).

Note: (1) First layer without wind.

(2) Fourth layer without wind.

(3) First layer with northeast wind, 5 m/sec.

(4) Four th layer with northeast wind, 5 m/sec.

Figure 6. Examples calculations from forecasting model

of Aoshio occurrence (DO concentration)

154
Results of Calculation

Simulation of Aoshio

Distributions of the DO calculated by our model are shown in Figure 6.

On the first layer without wind, oversaturations of DO are found in all areas

of Tokyo Bay except the mouth of this bay and the front of Funabashi. On the

fourth layer, anoxic water masses with DO concentration below 2 mg/1 cover

widely in the inner part of Tokyo Bay, and an anaerobic water mass is found in

front of Chiba Port. Next, the model with wind blow is expressed as follows.

After a duration of 2 days of northeast wind (5 m/sec), the anoxic water

mass is shown in front of Funabashi. The simulation model of an Aoshio occurrence indicates good accordance with observations in 1987 (Figures 2 and 3).

The areas with DO concentration below 2 mg/1 on the fourth layer are reduced

as compared with the model without wind. This phenomenon shows the effect of

upwelling of the anoxic water mass near bottom in the inner part of Tokyo Bay.

Relationship Between Current Pattern and

Contamination of Sediment in Tokyo Bay

In ozder to grasp the mean current pattern in Tokyo Bay, transport movement models are shown in Figure 7 during one tidal period. From the results

calculated, some conjectures concerning current pattern can be given as

follows.

a. The density currents produced by river runoff move from the inner

part of Tokyo Bay to its mouth on the first layer but show the pattern from the mouth to inner part on the fourth layer (Figures 7a and

7b).

b. Concerning the vertical movement of water, the remarkable descending

motions are found in the central part of Tokyo Bay in the case without wind. It may have effects on distributions of sediment and the

formation of an anoxic water mass. The organic matters discharged

from Tokyo Metropolis or Kanagawa Prefecture flow southward with the

surface current and gradually are descending offshore. As the currents on the lower layer flow northward, the environment near bottom

in the inner part is degenerated because of the long stagnation of

organic matter and its decomposition (Figures 7c and 7d).

c. As descending motions also are found in the central part of Tokyo Bay

with northeast wind, the same phenomena in the previous paragraph may

be supposed (Figures 7e and 7f).

d. Descending motions can be expressed, even with southern wind

(Figures 7 g and 7h).

As the mean state for long-interval flow, especially vertical motion,

might have an effect on sediment distribution, the relationship between descending flow and sediment was discussed as follows.

Ishiwatari (1988) studied the distributions of organic carbon in the

bottom sediment in Tokyo Bay. These results are shown in Figure 8. It was

155
oa kohaa, ,chihara

.- ", .ia~awt_ / // " = " S, aw_ ... 

0. OOHouA

10

a. Transport movement on first b. Transport movement on fourth

layer (constant flow without layer (constant flow without

wind) wind)

rsaraz -' " -s K azu

o. >ooo o o

c. Vrtalor motiont fom fsen d. Vrtalor motiont fom fourth

tofrstlr (constant toowthirdoulaers (constant o ihu

156

.nwind wind)

" - - -2 -1 -3 1 i 2 -

... .. isarazu .. . K isarazu

-s~~ _'o- 1*

.'okohama 1 Y'" oohama' '

)-CUDO. OOHOuR

C. Vertical motion from second d. Vertical motion from fourth

to first layers (constant to third layers (constant

flow without wind) flow without wind)

Figure 7. Simulation model of transport movement (Continued)

156
ra ;a'" ' -raya U . .. ..

. 7 , - - ii , ,- . I I 3 7

:IY oiharao a ......3a Ichihara

I0I

fa I F u b a h S h i nF .h u n a -b a . i . "

/:K-.., -, -I I:Z I ,. raz "-1" ..... . .

Yokhaa Ykoam 3 1

-6 ' ' -: ' ..... . ..... &

3S -. -- 3- Itra

1 -I 2 -1- 3

g.Transport o fou me 1 fo fourth

Figre0. (

0

C ud l ) .

157 ..

0. 00Oranpr moeet on fort0. 00 rtia Stio -ro3 ourth

e. rtansotmmntiourt f Ver o ial moratio fro indrt

Funabash i Funahash i 0

Ichkaw " hh~r, Ic ikw . . 1 -3.,, .. . chhr

Urayasu~ ..: . rys .

--- - - - - : - -' "- . . .

Shn OOOU w. OO u rS --

:3 - - - ,. . . . ..

g.Trnspotmovmentonfurt h. Vetia moio fro fourt

layer~~~~~~~~ lwwtKtihr (cntn aes(osantz

southwest~~~~ flwwt3otws 2id id

Fiur 7.Concluded 1 

Yoko ma . 1 31 S7
Arakawa :

Sumida.gawa ,

Tamagawa

7. ... . .. "OFigure 8. Distributions of organic

carbon in surface sediment in Tokyo Bay

(Ishiwatari 1988)

TOTAL ORGANIC

CARBON(0/0

... 0 _ 1 0k

determined that most parts of organic matter in the bottom sediment of Tokyo

Bay consisted of organic matter produced in Tokyo Bay, by comparison with carbon isotope data. By the col.parison of distributions of organic carbon

(Figure 8) with descending flow (Figure 7), it is obvious that a high concentration area may relate to distributions of descending flow in the central

part of Tokyo Bay.

As descending flow is produced by either northern wind or southern wind

in the central part of the bay, this flow may give suspending matters in water

an easy sedimentation condition.

DISCUSSION OF MANAGEMENT PLAN FOR AOSHIO

Management Plans

Management plans can be designed for each objective, as shown in

Table 2. Because the area of anoxic water mass appearance covers all interiors of Tokyo Bay, a big operation is needed to prevent an Aoshio from occurring. In consideration of environmental improvement, development of techniques, and utilization of the body of water, the possible operations to be

realized will be the improvement of bottom sediment through dredging and capping, removal of organic matter in water, and local improvement works for

special sites.

According to the results of the investigation in the past, the improvement of bottom sediment is the most effective method to realize the protection

against Aoshio. Thus, dredging and capping are suitable methods.

158
TABLE 2. OBJECTIVES AND COURSES OF STUDIES FOR PROTECTION

AGAINST AOSHIO OCCURRENCE

Objective Targets Management Plans*

Prevent Aoshio from Prevent anoxic water mass Dredging and

occurring from occurring disintegration of

stratified

structure

Prevent generation of Dredging and

sulfide disintegration of

stratified

structure

Prevent generation of Set up surface

offshore current by current adjustment

wind

Prevent generation of Set up bank on bottom

onshore current in

bottom

Protect the shell Make upwelling at Create ditches and

fishery distance from the shell banks

fishery

Protect the sea Make upwelling at Create ditches and

battling resort distance from the shell banks

fishery

Decrease frequencies Prevent anoxic water mass Sediment

of Aoshio from occurring improvement

occurrence

Removal of organic

matter

Removal of nutrient

loads

Accelerate mixing

aeration

Prevent upwelling Create submerged

banks and ditches

* Association of Fisheries Resource Protection in Japin (1978).

159
Since there are degenerated areas near the bottom, north of the line

connecting Honmoku (Yokohama) with Ichihara (Chiba Prefecture) in the Tokyo

Bay resulting from the input of contaminated discharges and the formation of

an anoxic water mass, the amendment regions have been determined by values of

COD and DO. These regions are shown in Figure 9.

Evaluation of Effects of Management Plans

Effects of management plans were calculated in three cases, namely, with

northeast wind, northwest wind, and without wind. In order to demonstrate the

effect of a management plan, the difference of DO values between the plan

(calculated plan) with hypothetical dredging and capping is compared with

present situation (Figures 10a and 10b). From these results, it is noted that

DO values after the management plan increase by 1.0 mg/2 over the value of the

present situation on fourth layer without wind. The areas of anoxic water

masoes are reduced.

'capping zone,'n

7dredging zone capping zone

Figure 9. Proposed areas for dredging and capping

160
Funabashi

Ichikawa,'

, hihara

Shi naawa - o..

Yokohama

mean ccrentration

during one tidal

period (mg/i)

a. Without wind

Figure 10. Increase of DO on fourth layer

after management plan (difference

between executing the management

plan or not) (Continued)

161
Ichikawa 

Funabashi

Shinagawa0

Yokohama

mean concentration

during one tidal

period (mg/I)

b. With northeast wind

Figure 10. (Concluded)

162
Following this model, the anoxic water mass disappears even in front of

Funabashi in spite of the suitable condition of Aoshio occurrence with northeast wind. In the example with northwest wind, the same phenomenon previously

mentioned can be obtained. Under various examinations with the management

plan, the areas of anoxic water mass calculated are exhibited in Table 3.

Although from this table areas of anoxic water mass without wind were

176 sq km concerning field data on fourth layer, they will be reduced to

28 sq km after the management plan. Thus, the effect of the management plan

should be verified by comparison with field data.

Annexation Effects with Management Plan

If dredging and capping are carried out with the same conditions under

the management plan, annexation effects in the following will be produced.

TABLE 3. AREAS* OF ANOXIC WATER MASS UNDER VARIOUS

CONDITIONS

Wind Conditions Layer

by Layer 1 2 3. 4

Present state

without wind 0 28 80 176

Present state with

northeast wind 8 44 60 92

Present state with

northwest wind 8 40 36 168

Management plan

without wind 0 3 4 28

Management plan with

northeast wind 0 8 4 16

Management plan with

northwest wind 0 8 4 16

* Values expressed in square kilometers.

Reduction of RegenerAtion from Bottom

Reduction values of regeneration from the bottom are shown in Table 4 in consequence of dredging and capping over 200 sq km. As noted, these values as

proposed are very effective and important.

163
TABLE 4. REDUCTION VALUES OF WATER QUALITY OVER THE AREAS

OF DREDGING AND CAPPING

Ratio for Ratio for

Reduction Value Regeneration Loading from

Parameter of Regeneration in All Areas Inflow

Item ton per day percent percent

COD 39.0 38 15

Total phosphorus 2.08 30 8

Effect of Water Quality Improvement

in Tokyo Bay

DO concentrations in summer will recover about 1 to 2 ppm than the preceding condition, and occurrences of anoxic water mass will be improved. COD

concentrations also will be improved over all areas of Tokyo Bay (lowering

about 0.3 ppm), and the transparency of water recovered will be about 0.3 m

higher than before. Under these conditions, it is possibly enough to show a

good living state for benthos.

Removal of Nutrient (Withdrawal of

New Sediment)

The removal of nutrient will be estimated to be 23.5 tons per day in

nitrogen and 5.4 tons per day in phosphorus on the supposition of a sediment

withdrawal of 1,270,000 cu m per year. These values correspond to about

9 percent and 27 percent for total loading of nutrients to the Bay, respectively. These results should contribute to the decrease of eutrophication in

the Bay.

Estimate Cost for Management Plan

The costs to realize this plan are calculated to be about 25 billion yen

($180 million US) in Table 5.

Synthetic Estimation

According to this management plan, it may be asserted to reduce remarkably the regeneration values from the bottom and provide some protection effect for Aoshio.

As the cost is estimated to reach an enormous value, the effects of this

plan do not remain for a long interval and will possibly diffuse widely over

all areas of Tokyo Bay. Now it is difficult to realize this plan as :he

national project.

164
TABLE 5. ESTIMATE COST FOR MANAGEMENT PLAN

Area Cost

Management Plan km2 million yen

Dredging 120 121.000

Capping 80 108.500

Withdrawal of new sediment 120 25.800

Total 255.300

To make improvement in water quality conditions ef Tokyo Bay, another

method also should Ne considered such as the curtailment of nutrient loading

from river and drainage. Recently, the recovery of natural environment has

encouraged interest from the global viewpoint. Following these currents in

the world, an increasing concern for this project is expected as one link of

global environmental problem.

CONCLUSION

The general scenarios of forecasting a model for Aoshio occurrence in

To!-yo Bay were elucidated on the basis of field studies in 1987. Tokyo Bay is

one of a few calm natural waterfronts left near the modern big city.

To apply this bay to fisheries or maritime recreaLiin, it is an urgent

problem to carry out the improvements of water quality ant bottom sediment

including protection of Aoshio.

The Second District Port Construction Bureau, Ministry of Transport,

would like to contirue the research and investigation in Tolyo Bay and

endeavor to realize this project.

REFERENCES

Association of Fisheries Resource Protection in Japan. 1978. "Guideline of

Design and Building for Arrangement and Development of Coastal Fishery Ground"

(in Japanese).

Chiba Prefectural Fisheries Experimental Station, Nori Culture Branch.

1987. "Information kbout Oceanographical Conditions in Tol.yo Bay," No. 62 (in

Japanese).

norie, T. 1987. "Nutrient Cycle Model and Its ApFlicatioa to the P~ediction

of Seawatec and Sediment:l Improvement," Report of the Pirt and Harbour

Research Institute, Vol 26, No. 4, pp 58-123 (in Japanese).

165

• A
Ishiwatari, R. 1988. "Sedimentation Process of Land-Derived Organic Matter

in Tokyo Bay," Bulletin on Coastal Oceanography, Vol 25, No. 2, pp 127-133 (in

Japanese).

Kataoka, S., Fuse, H., and Komatsu, A. 1988. "Aoshio in Tokyo Bay," Reclamation and Dredge No. 143 (in Japanese).

Samukawa, T., Ohta, K., Onizuka, M., Matsuo, S., Yamamoto, M., and Kon, I.

1987. "Studies about Aoshio in Tokyo Bay; No. 4, Discussion of Measurement of

Sulphur Particle Diameter and Examples of Measurement," Abstracts in the Fall

Meeting of Oceanographical Society of Japan (in Japanese).

Tokyo Metropolis, Chiba and Kanagawa Prefectures. 1988. "Results of Water

Quality Measurement in Public Sea Areas in 1987" (in Japanese).

10)
.ADPo 6 462

PROPOSAL OF THE SEA-BLUE PROGRAM--

APPLICATION OF NATURAL ENERGIES AND BIOLOGICAL

ACTIVITIES TO WATER QUALITY IMPROVEMENT ALONG COAST

Y. Hosokawa, T. Horie

Port and Harbour Research Institute, Ministry of Transport

1-1,3-chome, Nagase, Yokosuka 239, Japan

ABSTRACT

For waterfront development in inner bays, it is

essential to improve water quality so as to meet

social needs for comfortable coast environments.

A concept of creating a new water-affinity space

along a shallow coast is discussed with the consideration of sea surface as an attractive environmental

resource. Economical water purification should

harness natural energies (tide, waves, wind, etc.) as

well as biological activities (microbial film, macrophytes on tidal marsh, shells, etc.). Case studies

were also conducted and showed that our new idea

called "SEA-BLUE Program" will be feasible in the near

future.

INTRODUCTION

In Japan, social needs for easy access to comfortable waterfront

recently become stronger with the change of the life style of urban citizens.

In this paper, we propose a new concept to purify the surrounding water for

the waterfront to provide citizens with an environment more suitable to its

utilization. We try to apply the "goal-setting"-type approach instead of the

conventional "problem solving"-type one. From the strategic point of view, we

believe that the former approach is quite powerful for (a) awakening social

needs, (b) making aerial development concept, and (c) rearranging the present

technology more clearly to identify the objectives for technological development (Kondo et al. 1989). This approach also requires the consideration of

economical water treatment. We are trying to use natural energies and biological activities which are found easily at shallow coasts. For realistic

researches, we conduct some case studies of conceptual designs, which do not

necessarily mean real projects.

SOCIAL NEEDS FOR COMFORTABLE WATER SURFACE

Water affinity or accessibility can be categorized into the following

three levels: (a) watching the sea surface, (b) touching water by feet and/or

hands, and (c) bathing in the water. The utilization level will vary from

place to place depending on natural and social conditions as well as

167 92-10782

92 4 2l4llIIl 211116!it1
environmental conditions. Thus, the environmental goal to be achieved will

vary depending on each utilization level.

The Yokohama City Port Bureau conducted a survey of its citizens concerning the port affinity. The major part of the public coastal area in this

port is arranged for the watching level. They recognized the Port as an

attractive, enjoyable, and clear open place. At the same time, they also

pointed out the water pollution near the shore and inconvenience for marine

sports. They claimed, first of all, protection from the water pollution

rather than the traffic accessibility or the citizen's markets. The Prime

Minister's Office, the national government, made another survey for the visitors to ports and beaches. They were dissatisfied with the garbage on the

beach and the turbidity of water. A study of people's requests for waterfront

and regional development shows that "purification of organic contaminated

water alongshore" gets first priority (Figure 1).

These surveys make it clear that citizens expect a more comfortable

coastal environment and that the actual condition of the present coast near

urban areas needs some measurement to purify water. High water quality, which

is suitable for its utilization, is now requested even for the watching level.

On the other hand, improving the quality will promote utilization of the citizens as well.

BASIC CONCEPTS FOR CREATING COMFORTABLE COASTS

This report deals with the coastal sea water. The sea has its owu

attractiveness and gives much relief and comfort under well-arranged conditions. Five basic concepts for arranging conditions to achieve more attractive and comfortable scenery are described below.

The first concept is "encouraging natural characteristics of the sea."

The natural characteristics of the sea are, for example, enormous mass of

water, wide open surface, large relative heat and heat capacity, rich in salts

and ions, waves and tides, and various kinds of livings. All of these are

impressive and make us feel relaxed due to its width, the open sky with sea

gulls, cool fresh winds, salty smells, and regular sounds of waves and shells

on a beach. Even though it is much easier to improve water quality in a tiny

swimming pool, it is less comfortable.

The second is "creating and enhancing good conditions intentionally."

The sea has the potential in itself to attract people. Efforts are being made

to help express the attractiveness of the sea by managing the coastal environment. Port and/or beach protection facilities will be designed in a useful

way for improving water quality and accessibility.

The next is "making mutual connections between land and sea." Much

stress has been placed on the prevention policy from coastal disasters, such

as high surges, wave attacks, and Tsunamis. It often happens that people

living nearshore can hardly sea the water surface because of high seawalls.

The disaster prevention facilities should harmonize with the easy access to

the seawater. Floating bridges, artificial beaches, and offshore banks could

be ideas for improving accessibility.

168
/ 29.1% urification of

organic contaminated water

. along shore

- ---68.7%

harmonic landscape

I 22.3% 3817 persons

1 " 246.3%

_ (multiple answers)

side walk alog shore arranging play lot near shore

36.7%374

plning along shore

36.8%

Figure 1. Results of survey of people's requests for waterfront and regional

development

The fourth is "maintaining water quality suitable for its utilization

level." Water quality indices originally express the degree of inconvenience

for a certain utilization. The watching level requires less turbidity and

better smell quality, which is naturally different from the quality for bathing. Considering the utilization of coastal areas will mean identifying the

users who enjoy good circumstances. If the persons who should pay for improving environments can be identified, the cost-benefit relationship and financial planning could be discussed more easily.

The last is "combining countermeasures economically." The water quality

along the coasts is lower in concentration and larger in water mass than that

in the rivers and lakes. It is difficult to apply the techniques of the sewage treatment directly to coastal water. Copying purification functions of

169
the natural coast would be effective. Utilization of the natural energies and

biological activities is economical for us to promote and maintain higher

purification ability. This idea indicates a direction for the research and

development on environmental technology. This policy also introduces a way to

increase environmental capacity along the coasts from the viewpoint of environmental management.

VALUE OF ENVIRONMENTAL RESOURCES AND PROGRAMMING FLOW

Evaluating methods to determine the economical value of environmental

resources have been studied for a long time. The theory of willingness-to-pay

is a good stimulus. Now there is more interest in the whole image of programming flow, as shown in Figure 2. In Figure 2, all the feedback lines are

erased. This flow is composed of several ste ps from the object-setting to the

technical-solution, which is followed by the final goal of areal designing.

The process of each step is briefly described as follows;

* Step 1: Grasping social needs and present requests for the assigned

coastal area.

* Step 2: Research on the natural and social conditions and the present

environment.

* Step 3: Expressing the request as a catchword (e.g., the sea where we

can swim).

* Step 4: Making the object clearer by the selection of environmental

elements (water quality, sediment quality, current, wave, etc.) which

can affect and disturb the request sensitively.

* Step 5: Giving actual indices to the selected environment elements

and making them possible to measure (COD, turbidity, coliform, etc.).

* Step 6: Assigning each index an actual value or concentration which

suits the utilization of the water surface (COD <2 mg/1, coliform

<1,000 M.P.N., etc., for swimming level).

* Step 7: Choosing and combining technical measures to satisfy the

required environmental level.

* Step 8: Evaluating the requested level, techniques, and dimensions

from the viewpoint of designing feasibility.

For Step 7, the purification techniques are separated into three groups:

(a) techniques which remove or degrade pollutants from the water body (e.g.,

rock filter with biofilm, macrophyte vegetation, etc.), (b) techniques which

disperse or transport pollutants from the concerned area (e.g., regulation of

tidal flow by breakwaters), and (c) techniques which maintain or promote the

above two (e.g., construction of shallow marsh with macrophytes). Matrices of

various kinds of purification techniques, purification principles, and available natural energies are prepared, because these will be useful for the combination of techniques.

170
,gtep Istep 2

natural and

social needs social conditions

step 3

Fachword settin]

step 4

o n v i r onmentalI

element

K tep, 5

quality ,indices

/step 6

ective

concentration

step 7

chnical

combination

step 8

evaluation

Figure 2. Programming fluw

171
CASE STUDIES

Five areas for case studies were selected in order to give more actual

images to the programming flow. Two of the five areas are located at the

bottom of Tokyo Bay, and three along Mikawa Bay. These two are typical

eutrophic bays.

Ariake Area in Tokyo Bay

This area has abandoned shallow canals which were once used as the main

surface routes and stock surface for woods. It is located near the metropolitan area. The Tokyo Metropolitan Government has a rehabilitation plan for

this to be a residential area with office areas nearby. The water quality of

this canal is worse in summer (COD - 6 mg/1) due to the high primary production of plankton. The catchword is "harmonic symphony between sea and man at

urban oasis," which means introducing attractiveness of the sea into the urban

area. Water quality, accessibility, and landscape were selected as important

environmental elements to present a more comfortable waterfront. The utilization level is set as mainly watching (and touching at some part), and COD

(chemical oxygen demand) and DO (dissolved oxygen) are chosen for representative water quality. The objective standard assigned for these concentrations

were: COD <4 mg/2 and DO >2 mg/2 .

Areal designing principles are as follows: (a) leaving present water

surface as wide as possible to get better sight and landscape, (b) keeping

former breakwaters as they are because of dense natural woods on them, and

(c) arranging an artificial beach and marsh along the canal, a pedestrian

wall, and/or bridge over the canal to enable citizens to access water easily.

Figure 3 shows the zoning of this area. The water surface area is about

46 ha, and the water volume is roughly 1,000,000 cu m.

Rt .2 Rt.Harumi artificial marsh

Coastal

park western gate

old breakwater canal and

artificial small stream

atfcal beach residential --reclamation

gtarea 1 ( 50m

Figure 3. Facility arrangement of Ariake area

Technical considerations for the water quality and flow management were

made as follows: (a) dredging organic sediment followed by sand capping, the

most effective method of lessening nutrient concentration in the canal due to

its shallowness (mean depth, 2 m) and low water exchange, (b) enclosing the

canal water by east and west gates loosely to separate the improved water from

172
surrounding eutrophic water of the inner bay, (c) introducing surrounding

water after purification into the canal and making one-directional flow (from

the east island to the west gate) through the canal to exchange water

(hydraulic retention time, 50 days), (d) making small tidal movement (± 10 cm

above/below m.s.l.) in the canal to support the biological activity at the

artificial marsh, and (e) for above treatments (c and d), utilizing tidal

energy (tidal range for M2 component - 1 m) which is easy to pick up and rich

around this area.

Figure 4 is the schematic map of the water flow with the combination of

purification facilities. Purification facilities besides the capping include:

(a) artificial seagrass woods in front of the western entrance gate, (b) an

underground rock filter waterway under the pedestrian sidewalk, and (c) an

artificial marsh at the east end. The water mass intake is about

210,000 m3/day. Total area of the seagrass leaves is 3,200 M2 , expecting 20

or 25 percent solid separation efficiency. Total length of the rock filter

way is set at 1.5 km, expecting 60 percent removal of COD from the experimental result for fresh water (Horasawa 1979). A coagulation treatment process

can be applied, if necessary, after the rock filtration (33 percent removal

for COD and SS). Water quality can be evaluated by the numerical simulation

assigning the efficiency of each process. Predicted concentration of COD is

presented in Figure 5 for each option of the combinations. Option 1 shows

capping with 20 percent removal at seagrass woods and rock filtration. Option 2 expresses capping with 25 percent removal at seagrass woods and rock

filtration. Option 3 is added to a coagulation prccess after filtration based

on the second option. DO concentrations were calculated in the canal to make

sure that each DO is high above 2 m/1. The result showed that COD <4 mg/I can

be attained in this canal. A conceptual view of this areal development plan

is shown as Figure 6.

artificial marsh

rock filter I - . .

under pedestrian walk

ter sea water 4 3

L , m ....... _____ ___e_ ..............

intake*..v...

otfal "sand capping

sand intake

artificial j'cpige. 3

seagrass woods 4,000m /day_ ,

Figure 4. Schematic of water flow and purification facilities

(black arrow is water flow; white arrow is facility)

Yokohama Inner Port in Tokyo Bay

A river mouth at the inner port of Yokohama was chosen as a study area,

for this river has a waste treatment plant at the upper part and is the

173
watching level

3 touching level

0 X

u M'-

bathing level

0

area3 area.4 area 5 area6

present 0 option 2 [] condition oto

! option 1 [ option 3

"6

Figure 5. Predicted concentration of COD in each area (see

explanation of options in the text)

dominant pollutant source to the mouth area. This area (13 ha) is now surrounded by wharves and bank walls. Yokohama City has a big rehabilitation

plan called "Minato Mirai 21" (MM 21), and this water surface is expected to

be an open space with water affinity. But, in summer, the water quality (COD

5 to 6.5 mg/I, transparency 1.7 m) is not good enough for skin contact. The

catchword is "the creation of water affinity in the urban area." The objective is set as "touching," and transparency is selected for the environmental

element. The critical standard for this level is estimated as 2 m.

Dredging and capping are effective here, too. The water quality of the

bottom layer off Yokohama Port is low in COD and DO even in summer. Another

measure is to introduce this bottom water into the river mouth after aeration

by artificial falls or a fountain. A basic but expensive solution is to

lessen river load. Two measures are considered: partial sand filtration of

the river water at the upper point, and a change of the riverflow route near

the mouth. Three kinds of combinations (option 1: capping + introduction of

the outer water; option 2: option I + river purification; option 3: option I + change of the river route) are evaluated by numerical simulation. A

transparency of 1.8 to 2.2 m is obtained for option 1, and above 2.5 m for option 2. Option 3 wade a low-quality spot iithin the surface and is not suitable for our objective.

174
Q)

0

-4

co

2'1

41

Cu

"I

'-4

ICu

175i
Takeshima Island in Mikawa Bay

Both Takeshima and Ootuka areas belong to Camagouri City, which faces

the Mikawa Bay and is very attractive for its mild climate and long shallow

coastal line. Takeshima Island is famous for its beautiful sights and the old

shrine there. Many visitors from Nagoya visit this island and play at the

beach and coast near the island. However, the high seawalls and unpleasant

odor of drifted seagrass (Aosa) on the beaches are two unattractive features

to visitors. Water quality is good enough, for "touching level" at present.

"Come to Gamagouri" is a catchword for both Takeshima Island and Ootuka

beach areas. Important environmental elements for Takeshima Island are easy

accessibility to the beach and beach protection from drifting seagrass. High

productivity of the seagrass is a result of eutrophication of the Mikawa Bay.

Dredging and capping along the shore is the first measure. Flow regulation is

most effective for beach protection from seagrass. A flow generator from the

tidal energy is to be installed off the beach with deep trenches and curved

jetties for flow regulation. All these facilities will promote one-directional flow parallel to the beach. At the mouth of the flow generator, a

cropping stand with wire mesh fence will collect drifting grass. A numerical

simulation of drifting markers shows that 80 percent of the markers which

arrive at the beach under the present configuration are caught at the cropping

stand.

Ootuka Beach in Mikawa Bay

Another goal set was arranging the bathing beach with "bathing level"

water quality for the case study of this area. Bathing beaches along this

coastal line were difficult to find due to the eutrophication. A bathing

beach here is expected to increase visitor numbers. Representative environmental elements for this goal are COD of water quality and accessibility to

beach in harmony with prevention from high surge. The objective concentration

for COD is set as 2 mg/2 .

Water quality in surrounding water is 3 mg/1 in summer and a little different from the objective concentration. Then, the bathing area and artificial beach are designed to be enclosed by an offshore bank. This bank has a

wide crown (used as a pedestrian walk) and water purification ditches. The

tide makes head differences between the outer sea and the bathing area. At

flood tide, water from the outer sea is introduced into the bathing area

through purification ditches. At ebb tide, water from the bathing area goes

out through a submerged gate. Hydraulic retention time for this system is

estimated to be 1 week. Tidal range in the surrounding water is also estimated to be 30 percent as high as that in the outer sea. Numerical simulation

shows that the effect of the purification ditches is not enough to satisfy the

objective goal. Associated capping on the bathing area and some ecological

effect on a sand beach are needed to gain the high quality of COD <2 mg/2.

Tahara Area in Mikawa Bay

Tahara area is located on the Atsumi Peninsula, which separates Mikawa

Bay and the Pacific Ocean. This area has a long beach (1 km) facing the

eutrophic Mikawa Bay. Water quality in summer is COD 3 to 4 mg/i, which is

not suitable for bathing. Our goal is set to create a bathing environment

176
(COD <2 mg/i) for the wide water surface (L - 1 km and W - 500 m). At the

Pacific Ocean side, there is much clearer water (COD 1 to 1.5 mg/1) as well as

enough wave energy (H mean - 0.84 m). Using this wave energy, water introduction from the Ocean is planned. Waves (H >1 m) are collected by a shore slope

to get a higher elevation (+3 m). The outer water goes down across the Peninsula (6,500 m) to the receiving pond of the Tahara area. If flow of 7 m3/sec

is attained, the water quality in the bathing area becomes COD 1.5 mg/i. The

change of salinity concentration is calculated to be small. The total effect

to the whole Mikawa bay remains unknown.

CONCLUSIONS

Economical Point of View

An estimation of the required cost for the construction of purification

facilities at each study area was made, and the results are shown in Table 1

along with natural and social conditions. Our programming flow can be applied

for various natural conditions and water quality. When the results were compared, it was more expensive to improve the worse quality of the wider area,

as expected. Plans should be evaluated again for the area, and goals set on

the basis of cost.

Technical Objects

In Table 1, main facilities for environmental improvement are also summarized with each technical feasibility (from A, available now, to D, may be

available in the future). Among various ideas, the importance of biofilm and

flow regulation technologies is noted. Rules for the combination of facilities are also essential.

Environmental Management

A numerical study (Horie 1988) has already shown that changing the coastal features in an enclosed eutrophic bay affects the water quality near and

off the coast. Accumulation of the waterfront treatments for environmental

improvement will have a good effect on the water quality of the whole bay.

This effect will be estimated as an increase of the environmental capacity of

bay.

ACKNOWLEDGMENTS

This research was conducted with the advice of Professor Y. Goda, National University of Yokohama; Professor T. Sakoh, Tokai University;

Professor M. Shimizu, University of Tokyo; Associate Professor T. Maruyama,

Fishery University of Tokyo; and Associate Professor T. Kondo, Nihon University. We appreciate their advice and encouragements. We also express our

appreciation to the young ergineers of the Japan Sediments Management Association, who devoted their effort to the research and design. A part of this

paper was presented to the 36th Conference of Coastal Engineering, JSCE (Goda

et al. 1989).

1/7
TABLE 1. SUMMARY OF CASE STUDIES

rc chwon-d J envi ronmental

rtural (object level) proposed system for facilities vater

area main environmental improvement area/cost ouality

condition attractives (A-O:technical feasibility) (ha)(1O'YEN) improvement

gate C 0 D(mg/)

rhruonic 4-6.2

symphonyJ rock filter(C) 00 3.2-3.8

eutrophic 8 3

.2 canal D DO (ag/I) (i,'8tching) 89 1.4-7

capping(A) 3.3-8.8

side walk, artif icial grass woods (C) transparency

water park ,l0.8n

capping(A) introduction(A) C0D(W )

rwater 5-6.5

edaffinityi r - living filter(C) P0 4

river afiiy 1 3/ 8 D

" mouth D 0 (mW/)

0 (watching) 6 8 4-8 * 7.0

transparency

side walk, river ter 1.m boating treatment(A-C) o, Soo _ 1.8-2.5m

80% of

rCome to drifting

Gamagourii cropping grass

bopenach *, sad(B) 60 is removed

(touching) Takesh3i5

shell hunting flow

Takesima generator(C)

Shrine o 500

artificial marsh C3D(mg./l

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high 33

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(bathing) 7 3 6.1-9.6

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178
REFERENCES

Coda, Y., et al. 1989. "Proposal for Water Quality Improvement Programs irn

Harmony with Coastal Surface Utilization," -roceedings of Coastal Engineering.

JSCE, Vol 36, pp 884-88? (in Japanese).

Horasawa, I. 1979. "Purification Functions and Designing of Contact Aeration

Method," Water and Waste Water, Voi 21, No. 8, pp 88 893 (in Japanese).

Horie, T. 1988. "The Role of Modelling in the Control of Seawater Pollution," Wat. Sci. Tech., Vol 20, No. 6/7, pp 277-286.

Kondo, T. et al. 1989. "Triportopolis: A Concept for an Ocean-Based Multimode Transportation and Communic-tion Complex," International Symposium on

Coastal Ocean Space Utilization, New York.

179
THE PROBLEM OF DIOXIN CONTAMINATION IN SEDIMENTS OF THE PORT

OF NEW YORK AND NEW JERSEY AD-P006 463 J. F. Tavolaro, E. A. Stern

US Army Corps of Engineers, New York District

26 Federal Plaza

New York, New York 10278-0090

INTRODUCTION

The subject of this paper is the problem of dioxin contamination in

sediments of the Port of New York and New Jersey. The term dioxin describes

an entire family of chlorinated hydroc-rbon compounds. Figure 1 shows the

most problematic form of dioxin, 2,3,7,8-tetrachlorodibenzo-p-dioxin

(2,3,7,8-TCDD). When "dioxin" is referred to in this paper, it is this specific compound. It is a highly toxic chemical often formed as a by-product

during the manufacture of herbicides, wood preservatives, and other chlorinated hydrocarbon compounds. Also, it can be formed during paper bleaching

processes or due to incomplete pyrolysis of fossil fuels or municipal wastes.

Dioxin is extremely insoluble in water and shows a strong affinity to particulate matter, especially organic matter or fine-grained organic-rich sediments.

Exceptionally low doses, in the parts per trillion range, have shown a wide

range of toxic responses in laboratory test animals including carcinogenicity,

teratogenicity, fetotoxicity, reproductive dysfunction, and immunotoxicity.

Figure 1. 2,3,7,8-Tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD)

NAVIGATION IN NEW YORK HARBOR

Before the problem of dioxin in the Port of New York and New Jersey can

be discussed, it is useful to understand something about the Corps of Engineers' role in the Port. The New York District of the Corps of Engineers is

responsible for maintaining adequate navigable depths in the more than

240 miles of Federal channels in the Port. This maintenance work requires

dredging of approximately 5 to 7 million cu yd of mostly fine-grained

180 92-10783

42 2 4 217 I lll1l1J1I1!i1111111
sediments (muds) from these channels. Most of the dredging is accomplished by

mechanical means, usually clamshell dredging. The sediments are loaded onto

dump scows, and the scows are transported by tugboats to an offshore dump

site. When the site is reached, doors in the bottom of the scow open up and

deposit the sediment on the bottom of the sea. Since the early 1900's, harbor

muds from the Port of New York and New Jersey have been dumped in the same

general location approximately 6 miles offshore. This site !s called the Mud

Dump Site.

To determine if dredged material is environmentally suitable for ocean

disposal, US Federal Law requires that the sediment undergo rigorous bioassay

and bioaccumulation testing. Whenever there is good reason to believe that

the sediment contains significant levels of contaminants, it is tested. Benthic marine animals, such as shrimp, clams, and worms, are placed in samples

of the dredged material to be tested. Swimming marine animals, such as finfish and brine shrimp, are also subjected to the liquid and suspended particulate phases of the dredged material. These animals are monitored for a given

period of time to determine the levels of acute toxicity of the dredged

material. Animals still alive after the exposure period are analyzed to

determine if bioaccumulation of contaminants of concern has occurred, and if

so, the levels of the bioaccumulation. These test results are compared to

preestablished ocean disposal criteria to determine suitability for ocean

disposal.

It is with this understanding of the nature of the dredged material and

management of dredged material disposal practices from the Port of New York

and New Jersey that dioxin can now be discussed.

DIAMOND SHAMROCK COMPANY

Located in the northwest corner of the Port is a highly industrialized

waterway known as the Passaic River. On this waterway is the site of a former

herbicide plant known as the Diamond-Shamrock Company (Figure 2). During the

1960's this plant produced 2,4,5-T, which is one of the active ingredients in

the defoliant known as "agent orange," widely used during the Vietnam War.

Dioxin was produced as a by-product during the chemical processing of 2,4,5-T,

and huge quantities of dioxin-laden processing water were discharged into the

river. Over the years, dioxin concentrated in the sediments.

Only several miles downstream from this plant in Newark Bay are the

Ports of Newark and Elizabeth, one of the largest container port complexes in

the Western Hemisphere. In the mid-1980's the State of New Jersey Department

of Environmental Protection documented that certain commercially valuable

species of fish and shellfish in Newark Bay, New York Harbor, and the nearby

portions of the ocean contained measurable levels of dioxin in their tissue.

In several cases, the levels exceeded US Food and Drug Administration (FDA)

levels of concern of 25 to 50 parts per trillion (pptr). Concern was raised

that dioxin contamination was spreading to other adjacent waterways, including

Newark Bay.

181
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DIAMOND -

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Figure 2. Diamond-Shamrock Company on Passaic River

KILL VAN KULL/NEWARK BAY DEEPENING PROJECT

This issue was brought to a head when plans to deepen the Federal navigation channels that lead to the Ports of Newark and Elizabeth became a

reality (Figure 3). Environmental regulatory agencies were all concerned that

dioxin might be present in the dredged material in levels that could cause

harm to the ocean environment. The problem with addressing this concern was

that no one could tell what any level of bioaccumulation of dioxin meant in

marine animals. There was no clinical toxicological information available on

the effects of dioxin bioaccumulation in the ocean environment. Also, at the

time, it was not even possible to routinely test sediments for dioxin in the

parts per trillion range. In short, the knowledge or the technology was not

available to us to be able to evaluate the impacts of dioxin contamination in

sediments to the marine environment.

In order not to delay such an important dredging project for the Port,

another approach to the problem was taken. It was decided not to focus on

182
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1834
evaluating test results to determine the potential environmental impacts but

instead on disposal management techniques that would isolate the sediment from

the marine environment. Separate disposal areas were delineated at the Mud

Dump Site for the sediment from the deepening project and for the normal dayto-day dredged material. This way the potential problem sediment was

separated (Figure 4).

When the deepening project is completed, the dredged material is covered

with a thick layer of clean dredged material to isolate the potentially contaminated sediment mound and prevent it from coming in contact with marine

burrowing animals. The process of covering dredged material mounds is a

dredged material management technique called capping. This technique has been

the topic of several previous papers presented by my colleagues at past

US/Japan Technical Experts Meetings.

Our experiences with the deepening project made us realize the importance of learning more about dioxin. The problem was not going to go away.

In fact, the scope of the dioxin area appeared to be growing beyond the Newark

Bay drainage area. The New York District Army Corps of Engineers took the

lead, since it was the dredging program that was the catalyst for the need for

information. First, an Interagency Dioxin Committee composed of the involved

regulatory agencies was formed. The committee includes representatives from

each agency's regulatory compliance offices and their respective research

laboratories. Besides the Corps of Engineers, the agencies on the committee

are the US Environmental Protection Agency, US Fish and Wildlife Service,

National Marine Fisheries Service, and New Jersey Department of Environmental

Protection.

THREE-TIERED DIOXIN TESTING FRAMEWORK

The first task of the committee was to agree to a logical dioxin testing

and evaluative framework. The New York District proposed a three-tiered

testing framework (Figure 5). If there is a reason to believe that dioxin is

present, Tier 1 would involve testing the sediment for dioxin at a detection

level of I pptr. When the deepening project was being evaluated a few years

ago, it was not possible to achieve a detection limit of I pptr in sediments.

Because of recent state-of-the-art improvements in analytic techniques, these

detection limits can now be achieved. If dioxin is not present, no further

evaluation is needed. If it is present, a Tier 2 analysis is done.

In Tier 2, dioxin and total organic carbon concentrations in sediments

would be used in conjunction with a thermodynamic method of predicting the

maximum tissue bioaccumulation potential. The thermodynamic method involves

calculating the quantity of dioxin available for bioaccumulation as a function

of the relationship between total organic carbon and dioxin content in the

sediment and the lipid (fatty tissue) content in benthic marine species that

could come in contact with the sediment. Increasing total organic carbon

content in the sediment tends to decrease the bioavailability of dioxin, and

increasing lipid content in target animals tends to increase bioaccumulation

potential. The thermodynamic calculation balances the competition for dioxin

between sediment organic content and animal lipid content. It is an extremely

conservative approach and generally overestimates bioaccumulation levels.

However, it is for this very reason that it makes an excellent screening tool

to determine if real-time bioaccumulation testing is necessary on a

184
40 23.0' N

40 22.0' N

Zro

Figure 4. Mud Dump Site

185
BULK SEDIMENT TESTING

2,3.7.S-TCDD

TCDD ND lpptr

A !E25 pptr PROJECTED TCDD TISSUE > ppo

CONCENTRATION

50 pptr

10-DAY SOLID PHASE TCDD TISSUE ANALYSIS

>25 ppir >0--25 pptr

UNRESTRICT3ED UNSUITABLE OCEAN DISPOSAL

FOR WITH

OCEAN DISPOSAL OENDSOA OCEA DISOSALEXPEITIOUS XEIIU

CAPPING

Figure 5. Interim three-tier 2,3,7,8-TODD testing approach

case-by-case basis. Since bioaccumulation factors were not yet derived for

dioxin, the factors developed for PCBs were used in the thermodynamic

equations proposed for Tier 2. It was assumed that uptake behavior would be

similar since the two contaminants were chemically similar.

In Tier 2, the original proposal used evaluative criteria based on FDA

tissue levels of concern to interpret projected tissue levels of dioxin. The

FDA criteria are as follows:

a. For levels in fish below 25 pptr- -little cause for concern.

b. For levels in fish between 25 and 50 pptr- -restriction of intake to

no more than one meal of fish per week.

c. For levels exceeding 50 pptr- -the State should consider a ban on the

consumption of fish from these areas.

186
These criteria were transposed to an ocean disposal management

framework:

a. For all calculated tissue levels at 25 pptr or below, unrestricted

ocean disposal will be allowed.

b. For all calculated tissue levels between 26 and 50 pptr, only ocean

disposal with expeditious capping will be allowed.

c. For all calculated tissue levels above 50 pptr, proceed to a Tier 3

analysis.

In Tier 3, a 10-day solid phase bioassay/bioaccumulation analysis for

dioxin would be performed using a representative species for the environs of

the Mud Dump Site, the sandworm Nereis virens. For Tier 3, 25 pptr was proposed as the cutoff point. An average tissue concentration of less than

25 pptr in Tier 3 would be determined suitable for ocean disposal with expeditious capping. Any averaged tissue concentration greater than 25 pptr would

be unsuitable for ocean disposal at the present time.

The concept of this tiered approach was for the most part accepted among

the committee. The problems in implementing it revolved around three

questions:

a. Are the thermodynamic relationships expected in the Tier 2 calculations really true?

b. Will a 10-day bioaccumulation test be long enough to adequately

reflect steady-state bioaccumulation potential?

c. Is it realistic to use dioxin levels as high as 25 and 50 pptr as

decision levels in Tier 2 or Tier 3?

The bottom lime was that no laboratory data were available on bioaccumulation of dioxin upon which to base a realistic bioaccumulation test or thermodynamic calculation. Also, there were no field data on levels of dioxin

occurring in benthic marine species in the nearshore ocean that could be used

as the basis for bioaccumulation criteria.

DIOXIN BIOACCUMULATION STUDIES

To address these questions, two studies were initiated. The first was

designed to address the questions concerning the length of the bioaccumulation

test period and the validity of the Tier 2 thermodynamic calculations.

Specially designed tanks were used for long-term exposure of selected marine

species to sediment contaminated with dioxin. The objectives of the study

were to determine the bioavailability of dioxin from contaminated sediments,

measure the time required for tissue concentrations to reach steady state,

measure depuration rates, and evaluate the bioaccumulation factors needed for

developing a technically valid Tier 2 thermodynamic calculation.

The second study was designed to address the question concerning appropriateness of using dioxin tissue levels of 25 and 50 pptr as decision levels.

It was determined that the best way to address this question was to conduct a

181
survey of ambient tissue levels of benthic marine animals in the general

environs of the Mud Dump Site. The average amount of dioxin in the tissue of

animals that could come in contact with the dredged material would be used as

a point of comparison with the test results. If the dredged material testing

determines that the levels of bioaccumulation are less than the ambient dioxin

levels determined by the survey, then the dredged material may be acceptable

for ocean disposal.

DISCUSSION OF RESULTS

Although both studies have not yet been completed, there is enough information to make several conclusions. Figure 6 illustrates the most important facts. Shown is tle concentration of dioxin uptake in tissue (dry

weight) plotted against number of days of exposure to the contaminated sediment. Three species were exposed: Nereis virens (sandworm), Macoma nasuta

(clam), and Palaemonetes pugio (grass shrimp). Also shown by the dotted lines

is depuration of dioxin from subsets of the clam and worm populations that

were taken out of the exposure tanks on day 84. The total exposure periods

for the worms and clams were 180 and 120 days, respectively. The grass shrimp

was exposed for only 28 days. None of the animals was fed during the exposure

periods in order not to introduce additional "unknowns" into the experiment.

The grass shrimp could not survive more than 28 days under those conditions.

The uptake curves for the worms and clams show that although uptake of

dioxin is slow, both species reach a steady-state concentration eventually.

For the worm, steady state appears to be achieved between day 70 and day 120,

and for the clam, between day 28 and day 42. Before this experiment, no one

knew whether steady-state concentrations were ever reached. Previous dioxin

bioaccumulation studies in freshwater systems did not show that steady state

was ever achieved. These curves also show that most of the total bioaccumulation in the clams and half the total bioaccumulation in the worms occur in the

first 28 days of exposure. Thus, it is concluded that a 10-day solid phase

bioaccumulation test is nGt adequate. Exposures of at least 28 days are

needed for a meaningful test.

Another important conclusion can be inferred by observing the depuration

rates. The clams lost almost their entire body burden of dioxin within

42 days of being removed from the contaminated sediment. The worms are slower

in depuration, but they still lost half their body burden during the rpm-ainder

of the experiment, with no change in the downward trend. These changes show

that dioxin contamination in animals is reversible once exposure to the contaminant is eliminated and that isolating the animals from exposure to dredged

material, as is done when capping, is adequate to minimize the impacts from

dioxin contamination.

This uptake curve also gives us the information necessary to develop a

realistic thermodynamic equilibrium equation that can be used in a Tier 2

analysis. Before this curve was determined, it was assumed that dioxin bioaccumulation factors could be modeled after bioaccumulation factors already

experimentally derived for PCBs. This experiment confirmed our hypothesis

that PCBs were a reasonable model to follow, and a thermodynamic equation for

dioxin uptake can now be derived.

188
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189
Finally, concerni7.g the survey of ambient tissue levels in the general

environs of the dis,4sal site, data are still being evaluated. However, preliminary indications are that there is an average ambient level of dioxin in

benthic infaunal species of approximately 4 pptr. Perhaps this level of

bioaccumulation could be used as a starting point for discussions when determining if dredged material is suitable for ocean disposal.

CONCLUSIONS

In conclusion, some headway has been made in obtaining the knowledge

necessary to evaluate the potential ecological impacts of ocean disposal of

dredged material that is contaminated with dioxin, as summarized below:

A. Dioxin reaches steady-state concentrations in tissues of at least

some marine species.

b. A 28-day bioaccumulation test appears reasonable.

. Animals will depurate significant levels of their body burden of

dioxin once exposure to contaminated sediment is ended. This implies

that capping would work.

. Assumptions made concerning thermodynamic equilibrium models of bioaccumulation are shown to be accurate, and a resonable model can be

derived for dioxin.

. Finally, FDA levels of concern are probably too high to use as disposal criteria. Preliminary data indicate that 4 pptr may be a more

realistic bioaccumulation level to use based on ambient levels of

dioxin bioaccumulation in the environs of the disposal site.

190
NEW SOIL STABILIZER FROM THE COMBINATION OF INDUSTRIAL WASTES

AD-P006 464 M. Kamon, Associate Professor

A LJ'S. Nontananandh, Graduate Student

SDepartment of Civil Engineering

Kyoto University

Yoshidahonmachi. Sakyo-ku

Kyoto 606, Japan

ABSTRACT

This paper describes a potential partial utilization of certain types of sludgy industrial waste,

using a geotechnical engineering viewpoint. The primary objective is to investigate the potential for

burning various industrial wastes combined with lime,

in certain proportions, to produce a by-product having

hardening characteristics similar to ordinary portland

cement (OPC). The potential for using this new

cement-like stabilizer (NCS) for stabilizing loam soil

is then examined. It is found that the percentages of

main cementitious compounds in NCS, except alite (C3S)

compound, are higher than in OPC. The strength of

soil increases about 2 to 10 times that of remolded

unconfined compressive strength (i.e., 34.0 to

170.0 kN/m2) as the stabilizer content and curing time

are increased. The by-product thus shows promise for

use in stabilizing a loam soil for subgrade purposes.

Results are discussed in relation to the contribution

of ettringite in strength development.

INTRODUCTION

In recent years, researchers from various fields have attempted to solve

environmental problems posed by the production of industrial wastes. Gidley

and Sack (1984) suggested various methods of utilization of these wastes in

construction. Studies have also been carried out to investigate the possibilities of using industrial wastes such as slag, fly ash, sludge ash, and

crushed concrete powder in cement and concrete (Mehta 1985, Duda 1987,

Tay 1987, Dhir et al. 1988, Kamon et al. 1988). Potential uses for this

material include structural fill and subbase course for roads (Leonards and

Bailey 1982, Kamon et al. 1988). Recent projects illustrated that successful

waste utilization could result in considerable savings in construction costs

(Morgan et al. 1984, Jefts 1986).

Incineration is another way to eliminate problems of disposal of sludgy

waste materials containing oily and toxic materials. Chemical analyses have

shown that many modern industrial waste sludges are rich in main oxides such

as CaO, A120 3 (alumina), SiO2, and Fe20 3 (ferrite). It is therefore of great

191 92-10784 92 4 22111 lIf Ili1

92 4 24 2 18
benefit to the soil stabilization if this kind of waste can be converted into

a useful material. The primary objective of this study is to examine the

potential for burning various industrial wastes, of predetermined proportions,

to give a by-product which has self-cementing characteristics similar to ordinary portland cement (OPC). The potential for using this cement-like material

for stabilizing loam soil is then examined.

Experimentally, the approach used in this study consisted of X-ray diffraction (XRD) analysis and scanning electron microscope (SEM) observation to

investigate the main chemical compounds of an anhydrous stabilizer and the

reaction products produced in hydrated stabilizer and stabilized soil. Results of a laboratory investigation concerning the effectiveness of this new

type of stabilizer in comparison with OPC are evaluated using a measure of the

unconfined compressive strength (q,, strength), XRD analysis, and SEM

observation.

EXPERIMENTAL PROCEDURE

Material

Manufacturing Process and Some Characteristics

of a New Cement-Like Stabilizer

Producing stabilizers by combining industrial wastes was first reported

by Shida et al. (1987). Following their study, a new cement-like stabilizer

(hereafter refer to as NCS), derived mainly from various types of industrial

wastes, was produced. The raw materials of this new stabilizer include

sludges or cakes from a rubber factory (referred to as A factory), a sugar

manufacturing plant (B factory), and a brewery (C factory), as well as slag

from a steel manufacturing plant (D factory). All leachates complied with

water quality standards established by the Japanese Environment Agency \-3e

Appendix I), which permits their use as raw materials.

Two considerations are important in the preparation of raw materials for

NCS production:

a. Total amount of oxide.

b. Self-cementing characteristic.

The total amount of the main oxides, predetermined by using various proportions of waste materials, is used for the evaluation of hydraulic

properties.

The self-cementing characteristic is expressed in terms of the hydration

modulus, which is defined as the ratio of CaO to the summation of Si0 2 , A120 3 ,

and Fe203 . The hydration modulus is determined with reference to those of

alite and belite cement compounds, whose chemical compositions and calculated

hydration moduli are given in Table 1. As a target for material control, the

hydration modulus should be within the range of 1.7 (approximately corresponding to belite) to 2.4 (approximately corresponding to alite). It is for this

reason that CaO (in the form of lime) is added.

192
TABLE 1. CHEMICAL COMPOSITIONS OF CEMENT COMPOUNDS

Chemical Compositions (% by Dry Weight)

Compound CaO A1203 Si0 2 Fe203 Na20 MO K20

Alite 72.23 1.24 24.83 0.94 0.09 0.98 0.14

Belite 62.83 2.13 32.50 1.03 0.20 0.52 0.30

72.23 =26

Calculated Hydration Modulus of Alite = 7223= 2.67

1.24 + 24.83 + 0.94

Belite = 62.82 = 1.76 2.13 + 32.50 + 1.03

The proportion of raw mixtures was assigned to be A:B:C:D:Lime -

5:60:10:5:20. The calculation of chemical compositions for the raw mixture is

carried out by multiplying the percentage of main oxides illustrated in

Table 2 with the predetermined proportion. Table 3 shows the total amount of

each main oxide after combining, resulting in a hydration modulus of 1.78,

which is in the range of target values.

After all raw materials had been oven-dried, they were crushed and

weighed according to the predetermined proportion. The materials were blended

and compounded, and then burned under oxidizing conditions. (The analysis of

gas produced during burning was performed, but the generation of pollutants

such as NOX and dioxins was not found.) The chemical reactions and new crystals produced were dependent on a burning temperature, as highlighted in

Table 4. The resultant burned clinker was rapidly cooled in cooling water,

then sprayed with -50* C gas until the temperature was lowered to about

1000 C. Then it was removed from 1000 C environment and allowed to cool to

room temperature. The clinker was ground into powder having particle size

smaller than 0.075 mm and blended with gypsum to produce a hardening material

similar to OPC.

When compared with cement, NCS has a higher specific surface area but

smaller specific gravity: 4,090 and 3,350 cm2/g, and 3.07 and 3.17, respectively. The chemical compounds in NCS and OPC are given in Table 5. It was

found that the percentages of main cementitious compounds in NCS, except C3S

grain, are higher than in OPC.

As shown in Figure 1, the X-ray diffraction patterns for anhydrous and

hydrated NCS exhibit significant reductions of the 7.3 A C2S (dicalcium silicate), 4.9 A C2S, 3.5 A C3S (tricalcium silicate), and 2.7 A C3A (tricalcium

aluminate) peaks, and show increases of 9.7 A and 5.6 A ettringite peaks, as

well as the 3.00 to 3.02 A calcium silicate hydrate peaks, after having been

hydrated for 3 days. Observation by SEM supports the results by XRD.

193
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195
TABLE 4. CHEMICAL REACTIONS AND THERMAL CONVERSION PRODUCTS

CORRESPONDING TO EACH BURNING TEMPERATURE

Chemical Reaction Corresponding to

Burning Conditions Temperature (°C) Burning Temperature

100 - 110 Evaporation adsorbed water of

After igniting, the sludges

temperature is

increased to 8000 C Decomposition of sludges assoover a period of 450 - 800 ciated with diffusion of crystal

6 hr. water, resulting in weakening of

Si02 and A120 3 bonds

After holding 900 - 1,000 Beginning to form 2CaO • 7A120 3

the temperature at compound

8000 C for 2 hr, it

is increased to

1,200' C. 1,000 - 1,200 Forming 2CaO - Si02 • Fe203

compound

After holding 1,200 - 1,350 Forming 3CaO • A1203 and 4CaO

the temperature at A1 203 (clinker formation)

1,2000 C for 2 to 4 hr,

it is increased to 1,350 - 1,500 Forming 3CaO • SiO 2 and the clink1,500 ° C and held for ers have been completely melted

2 hr.

Cool immediately Will prevent a conversion of

a2CaO • Si02 to I formation

TABLE 5. CHEMICAL COMPOUNDS IN STABILIZERS

Chemical Compound (X)*

Stabilizer C2 S C2S C3A C4AF CaS04

NCS 19.6 35.3 27.1 6.80 6.30

OPC 63.2 12.9 11.6 4.00 3.30

• The following cement chemistry notations are used: C - CaO, A - A1203 ,

F - Fe 2 03 , and S - Si0 2.

196
603 days)

5 10 20 30 40 45

Diffraction Angle. 28 d ecree)

Figure 1. X-ray diffraction patterns for anhydrous and hydrated NCS

Figure 2 shows significant changes in mineralogical phases of NCS when mixed

with water (w/c - 0.5) and cured for 3 days. It can be noted that large C3S

and C2S grains disappeared, whereas ettringite abundantly covered the

surfaces.

Soil Material

Volcanic ash soils or loam soils are regional soils in Japan, widely

distributed over about half of the country. They possess certain characteristics causing some construction problems. Owing to the presence of a high

moisture content and organic matter (ignition loss - 11.6 percent), the

strength is considerably decreased when disturbed. The average remolded q.

strength is 20 kN/m 2 .

Upon visual examination, the soil has a yellow-brown color and contains

small amounts of fibrous root-plants. This soil forms individual clusters of

various sizes when desiccated. Results obtained from bID analysis show that

relatively high intensities are reflexed corresponding to peaks of quartz and

feldspar regarded as primary minerals. In addition, chlorite mineral is also

found as well as some amorphous materials. Further data on physical properties of the soil are given in Table 6.

Specimen Preparation and Tests

Specimens were prepared by mixing loam soil with a natural moisture con- tent and two types of stabilizer, NCS and OPCT The mix proportions were 3, 6,

9, and 12 percent by bulk weight. In accordance with the Japanese Society of

Soil Mechanic and Foundation Engineering guidelines, the following procedure

was used. Cylindrical molds measuring 5 cm in diameter by 0 cm in length

were used. After mixing, the soils were placed in molds in three layers.

197
a. Angular with fine to medium crystallines (10-40 pm) of C3 S and C2S, and

C3A and gypsum before hydration

b. Growth of ettringite and CSH on surface after hydration for 3 days

Figure 2. Changes in mineralogical phases of NCS

198
TABLE 6. PHYSICAL PROPERTIES OF LOAM SOIL

Sand fraction (2-0.075 mm, %) 25.2

Silt fraction (0.075-0.005 mm, %) 61.7

Clay fraction (less than 0.005 mm, %) 13.1

*60% finer (D60 , mm) 0.0275

Coefficient of conformity (U.) 6.60

Coefficient of concavity (U') 1.53

Natural moisture content (Wn, %) 86.4-90.0

Liquid limit (LL, %) 129.0

**Plastic limit (PL, %) 75.2

Plasticity Index (PI) 53.8

Specific gravity (Gs) 2.8/

Ignition loss (%) 11.6

Grain-size analysis.

** Consistency test.

Each layer was confined with a confining plate using static kneading energy to

reduce relatively large air voids. After molding, the specimens were weighed

to an accuracy of 5 g to confirm that the density was uniform at the beginning

stage. After approximately 18 to 24 hr, the molds were removed and the specimens were sealed by wrapping them tightly with thin plastic sheets, followed

by aluminum foil, to prevent loss of moisture due to surface evaporation.

Finally, for each sample proportion, specimens were cured at a room temperature of 200 ± 20 C and 80 percent relative humidity for periods of 3, 7, 28,

and 90 days, respectively. The specimens were subjected to the strength test

after the specified number of days.

The strengths were determined by an unconfined compression test using

the strained-controlled method at a constant rate of deformation of

1.0 mm/min. Moisture content was measured just after the initial mixing, and

after testing, by placing the soils in the oven at a drying temperature of

1100 ± 50 C for one night. Failures were also tested with a Rigaku X-ray diffractometer (using a Cu-target with a Ni-filter and input energy of 40 kV and

20 mA) and a JSM-840 scanning electron microscope to identify reaction products and to observe changes of the internal structure in the soil after

treatment.

199
RESULTS AND DISCUSSION

The development of soil strength when stabilized with NCS and OPC is

shown in Figure 3. It can be noted that the strength increases about 2 to

10 times the remolded q. strength (i.e., 34.0 to 170.0 kN/m2 ), as the stabilizer content and curing time are increased. In both mixtures the strength

does not change significantly at the low mix proportion (i.e., lower than

6 percent). It can be clearly seen that the strength gained when NCS is used

is about 1.5 times that gained when OPC is used at a mix proportion of 12 percent. Based on the results obtained, stabilized loam soil appears satisfactory for subgrade stabilization.

2.00

Mix

by" t) NCS OPC

3 0----0 *---

O}----0 in- -

1.50 12 0 -

0.50-- -- ---

0

/f

//

s i.oo -d

- (

0.50.. .

0 3 7 28 90

Curing Time (days)

Figure 3. Comparison of strengths obtained when

loam soil is stabilized with NCS and

OPC (values represent the average qu

strength of two specimens)

When results obtained from the strength test are compared to with those

from the XRD and SEM investigation, the addition of relatively small amounts

of stabilizers shows no noticeable changes. For this reason, it is most

likely that the reactions proceed at a slow rate. The development of strength

in this case is attributed to an agglometation caused by the exchange of Ca',

N+ , and H' ions.

200
In the presence of a greater quantity of cementitious compounds, the

reactions proceed more rapidly. This fact can be confirmed by investigating

X-ray diffraction patterns (Figure 4). The reaction products are identified

with a higher degree of crystallinity. Ettringite diffracted by X-ray at 9.7

A and 5.6 A are well defined at the initial stage of reaction. However, a

slight reduction in the intensities are noted after several months. The peaks

for calcium silicate hydrate (CSH) detected at 3.00 to 3.02 A are also apparent, while those anhydrous cementitious minerals gradually disappear after

further curing.

LEGENDS

4o : Mona orillonite

C :ChlIor ite

Et Ettringite

Q : uartz

: Feldspar

Ch CAH

F C3 CSS 1_ !Cc :CaCO,

Mo.C C Q

a 9 O-d a s cur ing

~ ~ 23- dAys curi~ng

~jI 4

Juki ' 7-dayi curing

F ~'. 64"f., 1 JF~\J 3-days curing

10 20 30 40 50)

Diffractioa Angle. 20 (degree)

Figure 4. X-ray diffraction patterns for loam soil after mixing,

and for mixtures containing 12 percent NCS aged for 3,

7, 28, and 90 days

The electron micrographs of loam stabilized with 12 percent NCS,

observed at 90 days, are shown in Figure 5. It can be seen that the needlelike crystals of hardened ettringite intercross between soil particles and

surfaces, filling up the spaces which, it is assumed, were previously filled

with pore water. Mehta (1983) found that ettringite of this form, known as

type I, was nonexpansive, but nevertheless contributed to enhancement of the

strength. Our previous work (Kamon et al. 1988) revealed that the strength

degradation due to the expansion of ettringite was not found when stabilized

loam soils were soaked for 24 hr (before qu strength test), and for 96 hr

(before California Bearing Ratio Test).

201
A.. . 1L i.ai;

Figure 5. SEM analysis of loam stabilized with 12 percent NCS

after 90 days, illustrating

intercrossing of ettringite

crystals between soil particles. (Et refers to

ettringite)

Figure 6 illustrates a semiquantative correlation between the strength

gained and diffraction intensity of ettringite, with all the treated specimens. It can be concluded that strength of the stabilized soils increases

with an increase of ettringite formation.

The observation just described thus brings to light another important

role of ettringite in stabilizing soil, other than the effects of ettringite

formation in portland cement concrete. It is believed that the contribution

of ettringite to the development of strength, particularly in soil with a high

moisture content, is mainly for two reasons. First, the crystals of

ettringite combine with large amounts of water, thus causing a significant

decrease in moisture content, which leads to an increase in the dry density of

stabilized soil. Second, extracting water that exists in pore spaces by

ettringite provides a reduced water ratio which aids further hardening.

Figure 7 shows that in the early stage there is a more significant reduction in moisture content in NCS-soil mixtures than in soil-cement mixtures.

If some amount of hydration water was combined to form ettringite, the moisture content was then partially decreased, according to ettringite formation,

resulting in a reduced water ratio of the phases. Since it was found that

ettringite was produced in higher amounts in NCS-soil mixtures than in soilcement mixtures, it was therefore concluded that a lower water-to-cementitious

ratio (w/c ratio) was obtained in the former. Consequently, the remainder of

the water that disappeared was assumed to be combined in the other reaction

products such as CSH, resulting in further reduction of moisture in the mixtures. This effect is found to be more enhanced in the NCS-soil mixtures,

compared to the soil-cement mixtures. Results from XRD as shown in Figure 8

substantiated that CSH was present at almost the same intensity in both

202
I ,0

1.50

0

1.00 i, 0,

"0

i 0

= I

/ 0 o 0.50 , Booo

0 NCS

[] o I(:

0-

0 100 200 300 400

Diffraction Intfn%1tv ( p%)

Figure 6. Semiquantitative correlation between strength and diffraction

intensity of ettringite for all

mixtures

mixtures, although it would have been expected that more would be produced in

the soil-cement mixtures, since it contained more C3S compounds.

CONCLUSIONS

Based on the experimental results, it is concluded that a new stabilizer

which is produced from the incineration of various proportions of industrial

wastes, combined with lime in specific chemical compositions, has selfcementing characteristics similar to OPC. It can be added to loam soil containing a high moisture content and organic matter for subgrade stabilization

purposes. The newly developed stabilizer has the following advantages:

a. Compared to conventional incineration, the developed technology described here provides a possible alternative for the treatment of

industrial wastes.

k. Converting the industrial wastes into detoxified and useful material

not only has environmental benefits, but also may conserve natural

resources by creating new materials for engineering construction.

203
100.00

90.00

(b 

.) 

OFw

80.00--------------- t

70.00

" - - - --.-.-. -.-...... ---0(- -.......-

" xN CS 0O11C

60.00- %b t

12---0 0- *

50.00 - t??

03 7 28 90

('1irin lime ( ,Ay-)

Figure 7. Observation of changes in moisture content with curing time

The results of this study bring to light some characteristics of ettringite in stabilizing loam soils. The crystals of ettringite play essential

roles in strength development because of the fixation of high amounts of

hydration water. This characteristic leads to an increase in dry density and

a decrease of the w/c ratio in the pore.

It may not be possible to eliminate the problem concerning the chemical

compositions of waste products which may change from time to time. However,

the quality of this cement-like material can be controlled by strictly checking the chemical compositions, particularly those of the main oxides, using

the calculated hydration modulus of 1.78 as a guideline, prior to each mix

design. Future plans include studying the effect of variation of the calculated hydration modulus, particularly at values approaching 2.4, which it is

believed would significantly improve the stabilized ,IdLtLial's strength.

ACKNOWLEDGMENT

The authors sincerely acknowledge their debt to Professor K. Akai of the

Department of Civil Engineering, Kyoto University, for his continuing

204
Q LEGENDS

Mo Nontsorillonite

C Chlorite

Et Ettringite

Q Quartz

F Feldspar

Ch CAH

Cs CSR

Cc :CaCO,

Mo.C Q

- 1000 Ch C CC

12 500

0 OPC

I I

10 20 0 40 50

Diffraction Angle. 26 (degree)

Figure 8. X-ray diffraction patterns for loam mixtures containing

12 percent NCS in comparison with 12 percent OPC after

3 days

encouragement. A special note of appreciation is expressed to Dr. A. Ohta and

Mr. Y. Shida of Tokiwa Kogyo Company, Ltd., for their cooperative efforts.

REFERENCES

Dhir, R. K., et al. 1988. "Contribution of PFA to Concrete Workability and

Strength Development," Cement and Concrete Research, Vol 18, pp 277-289.

Duda, A. 1987. "Aspects of the Sulfate Resistance of Steelwork Slag Cement,"

Cement and Concrete Research, Vol 17, pp 373-384.

Gidley, J. S., and Sack, W. S. 1984. "Environmental Aspects of Wastes Utilization in Construction," Journal of Environmental Engineering Division, ASCE,

Vol 110, No. 6 (December), pp 1117-1133.

Jefts, A. R. 1986. "New Runway Takes Off," Journal of Civil Engineering.

Vol 56, No. 12, pp 47-49.

Kamon, M., Tomohisa, S., Tsubouchi, K., and Nontananandh, S. 1988. "Reutilization of Waste Concrete Powder by Cement Hardening," Journal of the Japanese

Society of Material Sciences, Vol 37, No. 422, pp 1260-1265.

Leonards, G. A., and Bailey, B. 1982. "Pulverized Coal Ash as Structural

Fill," Journal of the Geotechnical Engineering Division, ASCE, Vol 108,

pp 517-531.

Mehta, P. K. 1983. "Mechanism of Sulfate Attack on Portland Cement

Concrete--Another Look," Cement and Concrete Research, Vol 13, pp 401-406.

205
Mehta, P. K. 1985. "Influence of Fly Ash Characteristics on the Strength of

Portland--Fly Ash Mixtures," Cement and Concrete Research, Vol 15, pp 669-674.

Morgan, D. S., et al. 1984. "Oil Sludge Solidification Using Cement Kiln

Dust," Journal of Environmental Engineering Division, ASCE, Vol 110, No. 5

(October), pp 935-948.

Shida, Y., Namba, K., and Takahashi, Y. 1987. "Developing a New Type of

Stabilizer Made from Industrial Wastes as Soft Ground Stabilizers," Proceedings of the 22nd JCSMFE, Niigata, Japan, pp 1881-1884.

Tay, J. H. 1987. "Sludge Ash as Filler for Portland Cement Concrete," Journal of Environmental Engineering Division, ASCE, Vol 113 (April), pp 345-351.

APPENDIX I. EFFLUENT STANDARD ACCORDING TO CLEAN WATER LAW

OF JAPAN TOXICITY TEST RESULTS

Maximum Allowable Concen- EA* Toxicity Test Results,

tration, in mg/1 per in mg/1 per liter

Contaminant lite: of extractant of extractant

Arsenic 0.5 <0.1

Cadmium 0.1 <0.1

Chromium 0.5 <0.1

Copper 3.0 <0.1

Iron 10.0 <1.0

Lead 1.0 <0.1

Manganese 10.0 <0.1

Nickel 3.0 <0.1

Zinc 5.0 <0.1

* Environment Agency of Japan.

206
DEVELOPING SEDIMENT QUALITY STAVDARD5:

COMPREHENSIVE SEDIMENT MANAGEMENT IN PUGET SOUND

C. C. Krueger

AD-POO 6 465 US Environmental Protection Agency

Hazardous Waste Division

1200 Sixth Avenue, HW-113 Seattle, Washington 98101

ABSTRACT

High concentrations of potentially harmful toxic

chemicals have been identified in the sediments of a

number of urban-industrial bays in Puget Sound. In

these areas, field studies have documented an increased frequency of fish disease, sediment toxicity,

alterP 4 benthic communities, and significant bioaccumulation of harmful chemicals in the edible tissue of

fish and shellfish. In response to this information,

and a growing public concern about the health of the

estuary, the Washington State Department of Ecology

has established a comprehensive strategy for sediment

management in Puget Sound. As a component of this

strategy, the agency is now in the process of developing a suite of sediment management standards for use

in a variety of regulatory programs. General sediment

quality standards are now available in draft form.

Once finalized and officially adopted, the standards

will be used to identify and designate sediments that

have adverse effects on biological resources or pose a

health risk to humans. It is anticipated that the

general sediment quality standards will also be used

as a basis for limiting industrial and municipal discharges, thereby preventing future sediment contamination. Separate, but related, sediment management

standards are also being developed for use in establishing cleanup goals for sediment remediation and in

making environmentally safe diecisions concerning the

disposal of contaminated dredged material. The

Department of Ecology will be using the apparent effects threshold approach, supplemented by the equilibrium partitioning approach, as the technical basis

for the derivation of the sediment standards. Field

validation studies indicate that these methods can be

used to generate chemical-specific standards which are

reliable predictors of adverse environmental impacts

associated with sediment contamination in Puget Sound.

These methods represent tools with potential widespread application.

92-10785

w24 24 219
INTRODUCTION

On December 29, 1987, the Washington State legislature adopted the Puget

Sound Water Quality Management Plan. Prepared by the Washington State Puget

Sound Water Quality Authority (PSWQA), in cooper&tion with the US Environmental Protection Agency (USEPA), this plan (known as the PSWQA plan), identified existing and emerging environmental problems in Puget Sound, established

environmental goals for the restoration and protection of the estuary, and

detailed specific actions to be taken by Federal, state, and local governments

toward achieving those goals. The PSWQA plan addressed a variety of environmental issues, including point and nonpoint source pollution, wetlands protection, environmental monitoring, and contaminated sediments. This paper summarizes the PSWQA plan's recommendations concerning sediment contamination, and

describes the comprehensive regulatory framework and technical approach currently being developed in Washington State to identity and manage contaminated

sediments in Puget Sound.

A COMPREHENSIVE STRATEGY FOR SEDIMENT MANAGEMENT

The PSWQA plan established a long-term management goal for sediment quality in Puget Sound. The goal, "to reduce and ultimately eliminate adverse

effects on biological resources and humans from sediment contamination

throughout the Sound by reducing or eliminating discharges of toxic contaminants and by capping, treating, or removing contaminated sediments," will not

easily be achieved. Sediments in many parts of Puget Sound, particularly the

nearshore, urban, and industrial areas, are currently contaminated with high

levels of potentially toxic substances, including heavy metals, polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons, and other organic

chemicals. The past and present sources of these contaminants are diverse,

including urban runoff and a variety of industrial and municipal discharges.

Field studies conducted in Puget Sound in the early and mid-1980s documented

increased prevalence of sediment toxicity, altered bottom-dwelling communities, and histopathological disease in fish and shellfish living in association with contaminated sediments. Recent evidence of significant bioaccumulation of cancer-causing chemicals in fish tissue has prompted several health

departments in the Puget Sound region to advise residents to limit their

consumption of locally harvested seafoods.

Past efforts to prevent sediment contamination and to identify, manage,

and clean up contaminated sediments in Puget Sound were hampered by the

absence of adopted state or Federal sediment quality standards or criteria.

Recognizing this void, the PSWQA plan identified an overall strategy for sediment management (PSWQA 1987). The strategy consists of four key elements:

a. Classification of sediments in the Sound that cause adverse

biological effects.

b. Implementation of Sound-wide source control to prevent future

sediment contamination.

c. Provision of rules and sites for the disposal of contaminated and

uncontaminated dredged material.

208
d. The development of guidelines for use in sediment cleanup actions at

heavily contaminated sites.

In response to this overall strategy, and the goals set forth in the

PSWQA plan, the Washington State Department of Ecology (WDOE) initiated the

development of a comprehensive sediment management program for Puget Sound in

1987. Integral to this program is the development of five categories of sediment management standards: (1) general sediment quality standards,

(2) effluent particulate discharge limits, (3) disposal standards for unconfined dredged material, (4) disposal standards for confined dredged material,

and (5) cleanup guidelines for sediment remedial action at highly contaminated

sites. These standards are currently in varying stages of development.

General Sediment Quality Standards

In December 1989, WDOE issued the general sediment quality standards in

draft form. The draft standards are now undergoing public review and comment.

WDOE anticipates formal adoption of the general standards by regulation, in

June 1990. Once adopted, the general sediment quality standards will serve

the dual purpose of (1) reaffirming the water quality goals (i.e., maintenance

and protection of human health and biological resources) already established

for Puget Sound in Washington State's water quality standards, and (2) identifying specific chemical and biological criteria (i.e., acceptable levels of

chemicals in sediments, bioassay toxicity limits) which must be met to ensure

protection of the beneficial uses of the estuary. As required in the PSWQA

plan, the general sediment quality standards will enable the identification

and designation of sediments that have acute or chronic adverse effects on

biological resources or pose a significant health risk to humans. It is currently anticipated that the standards will include chemical, physical, and

biological tests and clearly defined pass/fail guidelines for the tests. In

addition, the sediment quality standards will describe the intended use of the

chemical and biological tests and clearly defined pass/fail guidelines for the

tests. In addition, the sediment quality standards will describe the intended

use of the chemical and biological criteria and describe variance procedures

for a variety of regulatory programs. The methods that will likely be used to

identify chemical concentration limits for the general sediment quality standards are discussed in a later section of this paper.

Effluent Particulate Discharge Limits

The WDOE is also required by the PSWQA plan to develop procedures for

limiting discharges of pollutants to Puget Sound. The purpose of these procedures will be to ensure that future effluent discharges do not result in violation of the general sediment quality standards and that the potential for

future sediment contamination is minimized. It is currently anticipated that

final rules addressing effluent control limits and the relationship between

effluent control and the general sediment standards will be issued by WDOE in

June 1990. WDOE is currently considering a variety of approaches for enhanced

control of pollutant discharges, including, but not limited to, reliance on

best available technology, numerical limits on the toxicity of the particulate

fraction of the effluent, and numeric limits on the mass or concentration of

chemicals discharged. As part of the discharge management strategy, WDOE is

contemplating the establishment of sediment impact zones in wastewater

discharge permits. Conceptually, sediment impact zones would be similar to

209
dilution or mixing zones in the water column, and would be represented by a

limited area near a discharge point in which limited exceedance of sediment

quality criteria would be permissible.

Dredged Material Disposal Standards

The rules governing the management of dredged material in Puget Sound

are currently in various stages of development. Procedures and guidelines for

identifying disposal sites and for evaluating relatively uncontaminated sediment and disposing of the material at unconfined, open-water sites were established in 1988 as part of the PSDDA, the Puget Sound Dredged Disposal Analysis. PSDDA is a cooperative program sponsored jointly by the US Army Corps of

Engineers, the USEPA, WDOE, and the Washington State Department of Natural

Resources. The PSDDA sediment evaluation procedures, which combine chemical

evaluation of sediment and biological toxicity testing (PSDDA 1988), are now

being implemented in Puget Sound by Federal and state agencies. WDOE will

formally endorse the PSDDA standards for unconfined dredged material disposal

as part of the state sediment management strategy in July 1990.

Procedures for evaluating moderately to heavily contaminated dredged

material, and guidelines for safe disposal of this material in confined upland

or nearshore containment areas are currently being developed. As called for

in the PSWQA plan, the "confined disposal standards" are to be used by WDOE

and local governments in the dredged material permit process and shall address

treatment and disposal options for contaminated dredged material both in water

and on land. WDOE anticipates the adoption of the final confined disposal

standards in July 1990.

Sediment Remedial Action Guidelines

Finally, the PSWQA plan directs WDOE to develop standards for deciding

when heavily contaminated sediments should be capped, excavated, or otherwise

treated. The sediment cleanup remedial action guidelines which will serve

this purpose are currently being developed. When finalized, the guidelines

will specify chemical concentration trigger levels for use in identifying

sites for expedited remedial action. In establishing these guidelines, WDOE

is including consideration of the roles of source control and pollution prevention, natural recovery, and maintenance dredging in sediment cleanup. It

is not anticipated that all sediments which exceed the general sediment

quality standards will be subject to cleanup per the state remedial action

guidelines. Rather, the PSWQA plan allows that a distinction be made between

low to moderate exceedance of sediment quality goals and extreme circumstances

(i.e., exceedance of sediment remediation trigger levels) that warrant direct

intervention. It is anticipated that only the most heavily contaminated, and

thus the highest priority, sediments in Puget Sound will exceed the remedial

action trigger levels and be subject to expedited cleanup. It is anticipated

that WDOE will adopt final remedial action guidelines in June 1990.

EVALUATION OF METHODS FOR DEVELOPING SEDIMENT QUALITY STANDARDS

When the PSWQA plan first directed WDOE to develop a comprehensive program for sediment man&gement, it was understood that innovation would be required because of the absence of formally adopted Federal sediment standards

or criteria. It was also understood that the sediment assessment methods used

210
in standards development and source control in Washington State would likely

represent application of new and controversial techniques.

Over the past decade, a variety of techniques have been developed by

Federal, regional, and state agencies in the United States for evaluating the

significance of chemical contamination in sediments. Many of the early

efforts involved simple comparisons of chemical concentrations at contaminated

sites to concentrations in sediments from relatively unpolluted reference

areas. Later, more sophisticated methods were developed which not only incorporated consideration of sediment chemistry, but also attempted to establish

relationships between specific concentrations of individual chemicals in sediment and associated adverse biological and human health effects. As a first

step in developing sediment standards for Puget Sound, the WDOE and USEPA

evaluated a variety of field-based and laboratory-based approaches to establishing numerical sediment criteria. The specific methods that were considered by WDOE and USEPA are listed below.

Field-Based Approaches

* Reference Area Comparison. Sediment quality values derived based on

comparison of chemical concentrations at a site with concentrations

at an acceptable reference area (i.e., a relatively unpolluted site

with otherwise similar sediment characteristics).

* Field-Collected Sediments Bioassays. Sediment management decisions

made by exposing test organisms in the lab to field-collected sediment. Comparisons are then made between the mortality or sublethal

effects observed in field sediments and effects observed in experiments using sediment from a relatively unpolluted reference area.

Screening Level Concentration. Sediment quality values determined

using field samples to identify the sediment concentration above

which 95 percent of the enumerated benthic infauna species are

present.

* Sediment Quality Triad. Sediment quality values qualitatively

derived by analyzing relationships among contaminant concentrations

in sediment, the results of sediment toxicity bioassays, and the

characteristics of in situ benthic communities.

* Apparent Effects Threshold. Sediment quality values quantitatively

derived by using synoptically collected sediment chemistry, benthic

infauna effects, and sediment bioassay data to determine the chemical

concentration in sediment above which statistically significant biological effects are always observed.

Laboratory/Theoretically Based Approaches

* Water Quality Criteria/Interstitial Water. Concentrations of chemicals in sediment interstitial water are measured and compared

directly to the USEPA chronic water quality criteria.

211
* Sediment-Water Eguilibrium Partitioning. Sediment quality values

derived by using a theoretical model to predict the partitioning of

contaminants between sedimentary organic carbon and interstitial

water. Predicted interstitial water concentrations are then compared

directly to the USEPA chronic water quality criteria.

* Sediment-Biota Equilibrium Partitioning. Sediment quality values

determined by using a model to estimate the sediment concentration of

a contaminant that would be expected to result in a body burden of

the contaminant in benthic organisms exceeding a regulatory limit

(e.g., the US Food and Drug Administration limits for chemicals in

fish and shellfish).

* Spiked Sediment Bioassays. Test organisms are exposed to sediments

that have been inoculated with known amounts of chemicals.

Dose/response relationships are then used to identify chemical concentrations which do not result in adverse biological impacts.

Generally, the field-based approaches evaluated by WDOE and USEPA relied

on empirical observations of biological and/or chemical measurements to establish sediment quality values. Approaches such as the Triad and Apparent

Effects Threshold methods identified relationships between specific concentrations of chemicals in field-collected sediments and adverse biological

responses to exposed organisms. The laboratory/theoretically-based approaches

evaluated by WDOE and USEPA generally relied on extrapolation of Federal water

quality criteria to sediments, models of environmental interactions, or extrapolation of laboratory studies to develop sediment quality values. A more

detailed description of each of the methods listed above can be found in

Barrick et al. (1989) and USEPA (1989).

Comparison of Approaches

In evaluating the various methods for use in sediment standards development, WDOE identified 11 criteria that enabled objective assessment of the

approaches with respect to three important attributes:

g. Applicability of the approach to existing and planned sediment management programs in Puget Sound, including those identified in the

PSWQA plan.

b. Ability of the approach to generate criteria that are reliable predictors of adverse environmental effects.

c. Feasibility of implementation of the approach in the near term

(i.e., by 1990).

Specifically, each approach was evaluated based on the following 11

criteria:

a. Data requirements and cost of sediment quality standards development.

b. Cost of routine application as a regulatory tool.

c. Ability to develop chemical-specific sediment quality standards.

212
d. Ability to develop sediment quality values for a wide range of

chemicals.

e. Current availability of values for a wide range of chemicals of

concern in Puget Sound.

f. Ability to incorporate the influence of chemical mixtures in

sediments.

g. Ability to consider adverse effects on a range of biological

indicator organisms.

h. Extent to which the approach incorporates direct measurement of

sediment-associated biological effects.

i. Compatibility of approach to use of historical sediment chemistry

data.

j. Ease and extent of field verification in Puget Sound.

k. Extent to which the approach provides proof of a cause/effect relationship between concentrations of specific chemicals in sediment and

adverse biological effects.

Table 1 (adapted from Barrick et al. 1988) summarizes the results of

WDOE's comparative analysis. The table highlights the relative advantages and

limitations of each of the methods as gauged against the 11 evaluation criteria. For simplicity of presentation, each approach was assigned a subjective

scoring of "-", "0", or "+" to enable a relativc comparison based on each

criterion. A "-" has been assigned in cases in which an approach does not

meet the conditions of the criterion (e.g., relative to a cost criterion, a

method is expensive to develop); a "0" was assigned in cases in which an

approach somewhat meets the conditions of a criterion (e.g., an approach may

be moderately expensive to develop); and a "-" is assigned in cases in which

an approach substantially or fully meets the conditions of a criterion (e.g.,

an approach is not expensive to develop). In cases in which a criterion is

not appl.icable to an approach, "N/A" is assigned. A more complete analysis of

the adventages and limitations of each method and the scoring rationale for

each criterion can be found in Barrick et al. (1988).

Of the nine methods reviewed, two were considered by WDOE to be the most

promising for developing potential sediment quality standards for Puget Sound:

the apparent effects threshold (AET) approach and the sediment-water equilibrium partitioning (EP) approach. Descriptions of the AET and EP approaches

and a brief discussion of the technique used to field-validate sediment quality values derived from these methods are presented below.

Apparent Effects Threshold Approach

The AET approach estimates concentrations of a given sedimentary contaminant above which statistically significant (P - 0.05) adverse biological

effects are always expected (USEPA 1989a). The AET values for individual

chemicals or groups of chemicals are derived from actual sampling data and are

based on the statistical relationship between the contaminant level measured

213
d -H 0 + i.

+0

AA

00

~ .+

3.

4 t a a * . .

-6 a

* ..

S3 72

214~

A
in field-collected sediments and the results of biological tests conducted on

the same sediments. The approach is appropriate for use with any organic or

inorganic contaminant and does not require a priori assumptions concerning the

specific mechanism for interactions between contaminants and organisms (Beller

et al. 1986). AET-based sediment quality values can be developed for any

biological effects indicator that can be statistically evaluated relative to

reference conditions. Two kinds of biological effects indicators have been

used in developing Puget Sound AET: sediment toxicity bioassays and benthic

community evaluations.

The laboratory bioassays that have been used to date in Washington State

to develop AETs are the amphipod mortality bioassay (using Rhepoxynius

abronius), the oyster larvae abnormality bioassay (using Crassostera gigas),

and the Microtox bacterial bioluminescense bioassay (using Photobacterium

phosphoreum) (Barrick et al. 1988). Generally, these bioassays involve the

controlled laboratory exposure of test organisms to field-collected sediment

for a fixed period of time and an assessment of acute or sublethal effects

resulting from the exposure. Development of AETs based on indigenous biota

has been achieved by classifying and counting organisms found in sediment collected from contaminated areas and by then comparing the abundance of these

organisms to conditions in appropriate reference areas.

Figure I illustrates the derivation of a toxicity AET for lead. Each

square on the figure represents a sediment sample that was analyzed for lead

(and many other chemicals) and a hypothetical measure of adverse biological

response (e.g., amphipod mortality). All available sediment samples were

classified into two groups: (1) samples that did induce statistically significant adverse biological response (top bar), and (2) samples that did not

induce statistically significant adverse biological response (bottom bar).

Lead concentrations of samples within each group were then rank ordered by

increasing concentration. The AET was established by the station in Group 2

with the highest concentration that did not exhibit statistically significant

biological effects (660 mg/kg lead in this example). Above the AET, noncontradictory evidence exists that only significant biological effects were

observed in this data set. If the lead AET derived from this data set were

applied to an independent data set, it is expected that a high percentage of

samples with lead concentrations above 660 mg/kg would be associated with

toxicity to this test organism, or organisms of similar sensitivity.

The AET approach focuses on the fact that sediments can have concentrations of a given chemical as high as that chemical's AET and still have no

observed biological effects. Thus, it is assumed in the AET approach that

effects observed at concentrations below the AET for one chemical could have

resulted from unmeasured, covarying chemicals, interactive effects of multiple

chemicals, or other chemicals present at concentrations above their respective

AET values. The occurrence of biologically impacted stations at concentrations below the AET of a single chemical does not imply that AETs in general

are not protective against biological effects. Rather, the implication is

that single chemicals may not account for all stations with biological

effects. Field validation studies indicate that a high percentage of all

stations with biological effects can be accounted for by developing AETs for

multiple chemicals.

215
Lead

660 ppm SP-14RS1 RS-18

IMPACTED 4 4

foilI1 lulD 00

NONIMPACTED AET

1 10 100 1000 10000 100000

INCREASING CONCENTRATION -=

Figure 1. Derivation of AET for lead

Sediment-Water

Equilibrium Partitioning Approach

The EP approach is based on a simple model that describes the equilibrium partitioning of a contaminant between sedimentary organic carbon and

interstitial water, with little dependence on other physical or chemical

factors. A sediment quality value based on the EP approach is the sediment

contaminant concentration (organic carbon normalized) that would be expected

to result in an uncomplexed interstitial water concentration equivalent to the

corresponding USEPA chronic water quality criterion for that chemical (USEPA

1989b). If the predicted interstitial concentration for a given contaminant

exceeds its respective chronic water quality criterion, the sediment would be

expected to cause adverse biological effects. The approach is assumed applicable to a variety of environmental settings, including sediments with very

low total organic carbon content (USEPA 1988).

The primary advantage of the EP approach is that is uses the existing

EPA water quality criteria toxicological data base as a means of estimating

the potential for contaminated sediment to cause adverse biological effects.

Thus, use of this method does not require incurring the expense of collecting

new, site-specific biological data. For nonpolar organic compounds, the EP

model has a firm theoretical and empirical basis (USEPA 1988), and field

216
verification studies indicate that EP-based sediment criteria are reasonably

predictive (Read et al. 1989). For ionic, polar organic contaminants and

metals, the mechanisms controlling the partitioning of contaminants between

sediment and interstitial water are not fully understood. Therefore, the

ability of interested agencies to develop sediment quality standards for

metals and polar organic contaminants using the EP approach is currently limited. USEPA has initiated an extensive research effort to refine partitioning

models and to expand the utility of the EP approach to these groups of

compounds.

Overview of Approach to Field

Validation of Sediment Quality Values

Because none of the available approaches to developing sediment quality

standards are fully capable of addressing all concerns over interactive effects among chemicals and the effects of multiple chemicals on organisms, WDOE

and USEPA determined that field verification using diverse environmental samples was important to the evaluation of sediment criteria derived using the

AET and EP methods.

As means of testing the predictive reliability of the AET and EP approaches when applied to field situations, WDOE and USEPA conducted a series

of field validation studies (Beller et al. 1986, Barrick et al. 1988, Read

et al. 1989). In designing these studies, WDOE and USEPA acknowledged that

definitive confirmation of chemical-specific predictions would require additional controlled laboratory spiking studies. However, the costs associated

with a large-scale laboratory program addressing many chemicals was prohibitive. Furthermore, a feasible approach was not available for confirming that

the results of single chemical laboratory studies could be extrapolated, in a

meaningful way, to environmental samples which contained complex mixtures of

chemicals and represented a wide range of sediment conditions. As an alterna

tive, the agencies selected an approach to field validation which relied on

the use of AET and EP values to predict biological impacts associated with

contaminated sediments collected from the field. Data from approximately

330 stations, representing 13 embayments in Puget SourO, w-re coi;! into a

single data base. Each station included in the data base had been subjected

to extensive chemical analyses of the sediment and evaluated for sedimentassociated bioassay toxicity and/or effects to indigenous benthic organisms

collected from the field.

As the basis for the AET and EP evaluation, sediment chemistry results

for each station were compared to two different sets of AET and EP values for

a range of contaminants of concern. In the first evaluation, a comparison was

made for all chemicals detected in the Puget Sound data base and available for

either of the approaches (i.e., 12 chemicals for the EP approach and 60 chemicals for the AET approach). A second comparison was then made only for two

chemicals, total PCBs and phenanthrene, that were widely detected in Puget

Sound and common to both approaches. In both the complete and partial comparisons, exceedance of a chemical-specific AET or EP value for any one chemical

at a station resulted in a prediction that the results of the biological assessment at that station would indicate adverse biological effects.

During the comparative analyses, the AET and EP predictions were evaluated according to three measures of reliability: sensitivity, efficiency, and

217
overall reliability. Sensitivity was defined as the proportion of all stations exhibiting adverse biological effects that were correctly predicted as

impacted (i.e., all biologically impacted stations were identified as such by

the AET or EP predictions). Efficiency was defined as the proportion of all

stations predicted to have adverse biological effects that were correctly

predicted as impacted (i.e., all biologically impacted stations were identified as such by the AET or EP predictions). Efficiency was defined as the

proportion of all stations predicted to have adverse biological effects that

actually were impacted (i.e., ony biologically impacted stations were identified as such by AET or EP predictions). Overall reliability was defined as

the proportion of all stations for which correct predictions were made for

either the presence or absence of adverse biological effects. High overall

reliability results from correct predictions of a large percentage of the

impacted stations (i.e., high sensitivity, few false negatives) and correct

predictions of a large percentage of the nonimpacted stations (i.e., high

efficiency, few false positives) (Read et al. 1989). The concepts of sensitivity, efficiency, and overall reliability are illustrated in Figure 2

(Barrick et al. 1989).

As independent measures of reliability, sensitivity and efficiency are

important concepts to consider in selecting an approach to sediment management. A sediment standards approach that sets criteria for a wide range of

chemicals near their analytical detection limits will probably be sensitive

but inefficient. That is, it will predict a large percentage of sediments

with biological effects but will also predict, as impacted, many biologically

nonimpacted sediments with only slightly elevated chemical concentrations.

Such an approach may be environmentally protective but also may result in

overregulation that would not be cost-effective. Conversely, a sediment standards approach that sets criteria values at the upper end of the range of

environmental concentrations may be efficient but insensitive. That is, a

high percentage of the stations with predicted impacts may indeed be biologically impacted but the approach may fail to predict other biologically impacted stations with moderate to high chemical concentrations. Such an approach would be cost-effective and defensible in pursuing high-priority

remedial actions (i.e., would not result in overregulation) but wou]d not be

environmentally protective. The overall reliability of any method for establishing sediment criteria addresses both sensitivity and efficiency and provides perspective relative to the ability of potential sediment quality criteria to balance the need for environmental protection and cost-effective

environmental regulation.

Results of Field Validation

of Sediment Quality Values

The results of the field validation comparison using all available sediment quality values indicated that the Puget Sound AET (i.e., mixed organic

carbon/dry weight normalized AET for 60 organic contaminants and metals) had

generally reliable predictors of adverse biological effects. When evaluated

relative to the Puget Sound data base, the benthic AET values for the 60 contaminants demonstrated a 77 percent sensitivity, 100 percent efficiency, and

an overall reliability of 88 percent in predicting the presence or absence of

adverse biological effects in benthic infauna samples collected from 201 stations. Similarly, the sensitivity, efficiency, and overall reliability of the

218
OBSERVED PREDICTED

IMPACTS IMPACTS

0t

CORRECTLY PREDICTED

SENSITIVITY X a 5/8 x 100 x 63%

O+@

0

EFFICIENCY 9 5/7 x 100 - 71%

a. Sensitivity and efficiency

OBSERVED PREDICTED

IMPACTS IMPACTS

0 NO

IMPACTS

CORRECTLY PREDICTED -40-0

OVERALL 11/16 x 100 - 69%

RELIABILITY 0 + 0 *

b. Overall reliability

Figure 2. Measures of reliability

219
amphipod AET values were 55 percent, 100 percent, and 83 percent, respectively, in accurately predicting the presence or absence of amphipod mortality

in laboratory bioassays performed on samples from 287 stations (Read

et al. 1989).

In general, the sediment quality values generated using the EP approach

were less reliable than the AET-based values when evaluated relative to the

entire Puget Sound data base and all available AET. Taken in combination, the

EP values (i.e., organic carbon normalized mean EP values for 12 nonpolar

organic chemicals) demonstrated a 30 percent sensitivity, 65 percent efficiency, and 54 percent overall reliability in predicting adverse impacts to in

situ benthos. Similarly, the EP values demonstrated a 28 percent sensitivity,

51 percent efficiency, and 63 percent overall reliability, in predicting

amphipod bioassay mortality. The somewhat lower overall reliability of the

12 EP values in comparison with the 60 AET values is likely attributed to the

lower number of detected chemicals for which EP values were available relative

to AET values. Higher predictive reliability will likely be possible using

the EP approach when partitioning coefficients for metals and polar organic

contaminants become available for use in generating EP-based sediment quality

criteria.

The results of the reliability tests performed using 2njy phenanthrene

and total PCB values for the AET and EP approaches indicate that the EP-based

values are slightly more predictive than the AET values for these two contaminants. The demonstrated sensitivity, efficiency, and overall reliability of

the EP values in predicting adverse effects to benthos at 190 stations were

29, 65, and 54 percent, respectively, compared with a sensitivity, efficiency,

and overall reliability of 14, 100, and 52 percent, respectively, for the

benthic AET values. Similarly, the sensitivity, efficiency, and overall reliability of the EP-based values in predicting amphipod mortality in laboratory

bioassays were 27, 51, and 63 percent, rezpectively, compared with a sensitivity, efficiency and overall reliability of 3, 100, and 64 percent, respectively, for amphipod AET. The reduced sensitivity of AET-based sediment

quality values for total PCBs and phenanthrene, relative to the sensitivity

demonstrated when AET for all available chemicals were used, may reflect the

fact that there are a number of areas in Puget Sound for which other nonionic

organic contaminants, metals, or alkylated phenols are in high concentrations

in sediments and likely contributing to site-specific toxicity.

The results of the reliability analysis suggest that elements of both

the AET and EP approaches are useful in making environmental decisions. For

this reason, WDOE is proposing that the Puget Sound sediment quality standards

incorporate the best of both methods (i.e., that the standards for PCBs and

phenanthrene be EP-based and the standards for all other contaminants be AETbased). However, the results of the reliability analyses also suggest that

available chemical-specific sediment criteria alone may serve as incomplete

surrogate indicators of biological effects associated with unmeasured chemicals or the interactive effects of multiple chemicals. For this reason, WDOE

acknowledges that a combination o iological and chemical testing will be

necessary, in the near term, for e~tective management of contaminated sediments. In addition to EP- and AET-based sediment standards, WDOE will be

requiring confirmatory, site-specific biological testing as part of the

general sediment quality standards for Puget Sound.

220
CONCLUSIONS

Chemical contamination of marine and estuarine sediments in developed

coastal areas is a significant problem not only in Puget Sound but also

throughout the United States and internationally. The regulatory framework

adopted by EPA, PSWQA, and WDOE for sediment standards development and implementation in Puget Sound will likely be the first such comprehensive program

in the United States and it may well serve as an appropriate model for sediment management elsewhere. The AET and EP approaches, used as methods for

establishing sediment quality standards, also have potential widespread application. The AET- and EP-based sediment quality values appear to be reasonably

predictive in Puget Sound and can be generated independently for other locations. Supplemented by limited site-specific biological testing, AET- and

EP-based sediment quality values provide a defensible basis for regulatory

decisions concerning the identification, management, and cleanup of contaminated sediments.

For additional information on the comprehensive sediment management program being developed by WDOE, please contact Mr. Keith Phillips, Washington

Department of Ecology, Sediment Management Unit, PV-II, Olympia, Washington

98504. For additional information on the AET approach, please contact

Ms. Catherine Krueger, US Environmental Protection Agency, Hazardous Waste

Division, HW-113, 1200 Sixth Avenue, Seattle, Washington 98101. For additional information on the EP method, please contact Mr. Christopher Zarba,

Environmental Protection Agency, Office of Water Regulations and Standards,

WH-585, 401 M Street S.W., Washington DC 20460.

REFERENCES

Barrick, R., Becker, S., Pastorok, R., Booth, P., and Jacobs, L. 1989.

"Contaminated Sediments Criteria Report," prepared for the Washington State

Department of Ecology, Sediment Management Unit, by PTI Environmental Services, Bellevue, WA.

Barrick, R., Becker, S., Pastorok, R., Brown, L., and Beller, H. 1988. "Sediment Quality Values Refinement: 1988 Update and Evaluation of Puget Sound

AET," prepared for Tetra Tech/US Environmental Protection Agency, Region 10,

Office of Puget Sound, by PTI Environmental Services, Bellevue, WA.

Beller, H., Barrick, R., and Becker, S. 1986. "Development of Sediment

Quality Values for Puget Sound," prepared for Resource Planning Associates/US

Army Corp of Engineers, Seattle District, Puget Sound Dredged Disposal Analysis and the Puget Sound Estuary Program, by Tetra Tech, Inc., Bellevue, WA.

Puget Sound Dredged Disposal Analysis. 1988. "Evaluation Procedures Technical Appendix," prepared for Resource Planning Associates/US Army Corp of Engineers, Seattle District, Puget Sound Dredged Disposal Analysis, by Tetra lich,

Inc., Bellevue, WA.

Puget Sound Water Quality Authority. 1987. "1987 Puget Sound Water Quality

Management Plan," Seattle, WA.

221
Read, L., Jacobson, M., and Barrick, R. 1989. "Application of Equilibrium

Partitioning Sediment Quality Criteria to Puget Sound," prepared for the Washington Department of Ecology by PTI Environmental Services, Bellevue, WA.

US Environmental Protection Agency. 1988. "Draft Briefing Report on the

Equilibrium Partitioning Approach to Generating Sediment Quality Criteria,"

submitted to the EPA Science Advisory Board by the USEPA, Office of Water

Regulation and Standards, Criteria and Standards Division, Washington, DC.

US Environmental Protection Agency. 1989a. "The Apparent Effects Threshold

Approach," Briefing report to the EPA Science Advisory Board, prepared for

Battelle/USEPA, Region 10, Office of Puget Sound, by PTI Environmental

Services, Bellevue, WA.

US Environmental Protection Agency. 1989b. "Sediment Classification Methods

Compendium" (draft final report), prepared for USEPA, Watershed Protection

Division, by Tetra Tech, Inc., Bellevue, WA.

222
SOLIDIFICATION TECHNIQUE FOR DREDGED BOTTOM SEDIMENTS

N Wado

D-P00 466 46Japan Chief of the Engineering Committee

Sediments Management Association IIIIIIIIIIIIIIIIIIIIII 2-7-12 Tsukiji, Chuo-ku, Tokyo 104, Japan

ABSTRACT

Bottom sediments, which cause pollution in the

sea, river, and lake, have high fluidity and contain not only many organic matters with bad odor

in general, but also toxic heavy metals in some

circumstances.

Now in Japan, since many regulations and restrictions have been published for disposal of

such sediments in the area of concentrated population and high utilization of land, it is highly

necessary to stabilize the dredged sediments speedily and to provide the disposal area.

This paper presents the solidification technique for dredged bottom sediments which was

developed and practiced popularly in Japan for

the above purposes.

INTRODUCTION

"Bottom sediments" are so-called "HEDORO" and defined as particles,

which were in general produced through natural agencies or human activities,

and then accumulated at the bottom of the lake, river, and sea. It is noted

that "waste sludge" is produced through wastewater disposal at the facilities

for water supply and sewerage and various factories. In this paper, "bottom

sediments" include both bottom sediments and waste sludge. The solidification

system is reported as one of the bottom sediments treatment systems which have

been applied to dredging for purification of the environment and maintaining

the water capacity.

PROPERTIES OF BOTTOM SEDIMENTS

Bottom sediments generally have the following properties:

a. High water content and high percentage of silt and clay particles.

b. Often include organic matters.

c. Include toxic substances in some cases.

223 92-10786

4V24 220l 111 111 1111 I11 II till li
d. Have bad odor in some cases.

"Solidification technique" has been applied to one of the treatment

systems in order to make the handling of bottom sediments much easier.

PURPOSE OF SOLIDIFICATION

First, in order to remove water from the bottom sediments to be handled,

a lot of energy and a long consolidation time are required. Second, in order

to minimize the leaching of toxic substances and the occurrence of the bad

odor, chemical treatment shall be required.

The above conditions can be solved by the application of the solidification technique for bottom sediments. Objectives of this technique are as

follows:

a. To prevent "splash out" during the transportation of dredged sediments to the disposal area.

b. To enable direct placement of dredged sediments on the disposal area.

c. To allow trafficability for the construction machines on the disposal

area.

d. To utilize the dredged sediments as banking or filling materials.

e. To lock and minimize the leaching of toxic substances.

f. To reduce the bad odor.

g. To stabilize the foundation of structures constructed on the disposal

area.

CHARACTERISTICS OF SOLIDIFIED SEDIMENTS AND

THEIR REQUIRED STRENGTH

The required strength and other characteristics of solidified sediments

to accomplish each purpose are shown below:

Handling and Transportation of Sediments

Unconfined compressive strength (q,) for transportation by truck with

30 km/hr in average speed, 20 percent of unpaved roads out of total route, and

3-hr transportation shall be classified as follow:

A. q. 0.3 kgf/cm2 : easy for transportation.

b. 0.05 : q, < 0.3 kgf/cm2 : occasionally difficult (depending on the

sediment properties and transportation condition).

g. qu : 0.05 kgf/cm2 : very difficult for transportation.

A very small value of qu (less than 0.05 kgf/cm2) can be estimated by the

fall-cone test (F,). In a practical case, q,, is usually specified as the

224
value between 0.5 kgf/cm2 and 1.0 kgf/cm2 because of the variety of the properties considered.

Surface Laying on the Disposal Area

Bottom sediments soon after dredging are very soft with the qu value

ranging from 0.04 kgf/cm2 through 0.06 kgf/cm 2 . Even though such sediments

will gradually consolidate, using the bulldozer takes too long for surface

laying of sediments on the disposal area. Once surface laying is tried on the

disposal area soon after dredging, sediments will easily liquify and flow out.

In this case, forming a solid surface layer by solidification is so effective

that surface laying work can be well executed, as shown in Figure 1. The design flow diagram for the surface solidification method is presented in

Figure 2. This involves the following activities:

a. Check the stability by the circular sliding method.

b. Study the stress condition in the layer.

(1) Ultimate design method for the case of more than 1 tf/m2 in

shear strength.

(2) Coefficient of the subgrade reaction method for the case of

less than I tf/m2 in shear strength.

c. Check the bearing capacity of unsolidified subgrade for the subgrade

reaction due to the load.

Dredged Sedinient Surface Laying Work

Solidified Layer////

Thickness of Disposal Area

Original Seabed

Figure 1. Solidification for surface laying work

Trafficability on Disposal Area

The required solidified strength for trafficability of the construction

equipment working in the disposal area depends on the dimensions of the machines and is generally qu equals 0.5 - 1.0 kgf/cm2 . The relations

between the kinds of construction equipment and the required cone index (qr)

are shown in Table 1. Other relations between cone index (q) and unconfined

compressive strength (qu) are plotted in Figure 3.

225
s Tr A Rz r

Wi d th. Thi ikness & S treng th

o soiidl'fia( layer

Calcalation or Cir-cular

sliding failure

Yes

Coefficient of Subgradlc

UItc iiima [ c1 Des i goi Me It o d Rc ac [i oi Me thIiud

S u1)g ra (I evactL i oni B enid ingF stLr ess.

by lious;i nesq Method Shearing Stress.

Subgrade Rleaction. [ Set t LI cinen L.

Yes

Strss sYeul

Calculationi of Bearing Capacity

by JAA Method

1)unitchIting Shear

Y e

---- SUW, r adc ReactL i oni N o

~~-Rv[lar inn apc

C T1 0 11

Figure 2. Flow diagram for the surface solidation method

226
TABLE 1. CONSTRUCTION MACHINE AND THE REQUIRED CONE INDEX

Cone Index, qc

Construction Machine (kgf/cm2)

Speci.l swamp bulldo . 2

Swamp bulldozer 3

Bulldozer (medium class) 5

Bulldozer heavy class) 7

Scrape-dozer 6

Pulling-type scraper >7 (swamp type 4)

Motor scraper a10

Dumptruck 12

10 0

9-

8-

,7

0 0. 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 Lit 1.2

Uncanfinled Comnpressiye Strength qc(ky f,/cd)

Figure 3. Cone index and unconfined compressive

strength

Since the contact pressure of the construction machine is often used,

the relation between contact pressure (P) and required cone index (q=) is introduced as follows.

The bearing capacity of subgrade with 4 (internal friction angle) - 0

can be expressed below by Terzaghi's Bearing Capacity Formula:

227
qd - cN.

where

qd - ultimate bearing capacity of subgrade (kgf/cm2)

c - cohesive strength (kgf/cm2

NC - coefficient of bearing capacity (Nc - 5.3)

Supposing that q. - 1/6 - q , the relation between qd and qc is written

as

qd cNc

-1/12 • q, " 5.3

0.44 q,

Using contact pressure (P) and safety factor (F.) for ultimate bearing capacity (qd), the relation between P and the required cone index (qc) is expressed as

q. qd/0"44

F5* .P/0.44

An example case of P - 0.7 kgf/cm2 and Fs - 3 is shown below.

q- 3 x 0.7/0.44

- 4.8 kgf/cm2

Utilization as Banking

or Filling Materials

Modulus of deformation is one of the characteristics which indicate the

applicability to the construction materials. The strength of solidified soil

gradually varies from plastic behavior in the early stage to rigid behavior.

Stress-strain curves of three typical soils are shown in Figure 4. Soft

clayey soil (curve a) has a high plasticity, and is strained considerably even

under little stress. Sandy soil (b) has less strain than soft clayey soil,

and solidified soil (c) has a peak stress under a little stress.

The tangent modulus of elasticity of each soil in Figure 4 may correspond to the modulus of deformation, which can be calculated by dividing half

of the peak stress by relevant strain. The modulus of deformation of solidified sediments can be one of the indices for applicability to banking or filling materials. Table 2 shows the moduli of deformation of various kinds of

construction materials.

228
/

/

/ Solidiied Soil

/7

C .7

Sandy Soil

b

a Sort Clayey Soil

Strain e (Y)

Figure 4. Stress-strain curves of soil

Removing Bad Odor

Each bottom sediment has its own peculiar smell which originates in the

chemical production of hydrogen sulfate gas, etc., as a result of the activity

of bacteria in bottom sediments. During the process of solidification by

cement-type chemicals, the hydrogen-ion concentration (pH) of the bottom sediment increases to about 12. Under such a strong alkalic condition, sulfate

gas, which mainly causes the bad smell, is not produced at all because of the

production of calcium sulfate, as shown below.

Free H2S in liquid phase of sediment - H+ + HS4 Adding Ca(OH)2 which is contained in cement-type chemicals

Ca(OH)2 + H2S - Ca2+ + 20H- + 2H+ + 2S2-

-CaS + 2H20 + S2 -

The equilibrium of pH and sulfate (H2S) during the above chemical reaction is

shown in Figure 5.

There is a test report of odor removal for bottom sediment at Tangonoura

in Japan where sulfate (H2S) gas from bottom sediment caused serious pollution. In this test, 100 g of CaO was added to 10 kg of sediment and mixed for

5 min with 50-rpm churning. After 15 min, the smell of sulfate gas was completely removed, and the dark brown color of the original sediment had

disappeared.

229
TABLE 2. MODULI OF DEFORMATION OF CONSTRUCTION MATERIALS

Construction Material Modulus of Deformation

Soil - 100

Sand 100-500

Mixture of gravel, sand, and clay 500-2,000

Crushed stone 500-2,000

Soil cement 10,000

Pit sand 500

Crusher-run 1,000

Graded crushed stone 1,000

Cement-stabilized soil 15,000

Lean concrete 40,000

Bituminous macadam 2,500

Slag 1,000

Graded crushed stone 3,000

Crusher-run 1,100

Sand 350

Soft clay 5-40

Normal clay 40-80

Loose sand layer 80-150

Stiff sand layer 100-200

Compacted sand layer 500-800

Compacted gravel layer 1,000-2,000

230
100 1 1 1

112 S HS80- 

SZ-

'- 60

CU

0

6 7 8 9 10 pll

Figure 5. Equilibrium of pH and sulfate (H2S)

On the other hand, once bottom sediments become alkalic, ammonium salts

in the sediment can decompose and the resulting ammonia gas smell is offensive. Since ammonia is soluble and its solution shows weak alkalinity, neutralization by misting a weak acid (e.g., A12 (S04) solution) over the alkali

sediment is effective in removing this odor for a certain period.

According to current Japanese regulations, eight kinds of substances are

restricted, as shown in Table 3.

Reduction of Teaching

of Toxic Substances

In solidification of bottom sediments using cement-type or lime-type

chemicals, the calcium ion in the chemicals has a chemical-fixing effect on

toxic substances in the sediments as well as a pozzolanic effect.

As the density of hydration ions (OH-) in the solution becomes high, and

the liquid phase is alkalized, the metal ion (M') in the solution is changed

to hydrated metal with sedimentation through the following reaction:

M+ + OH- - MOH

231
TABLE 3. REGULATIONS FOR SUBSTANCES OF BAD ODOR

Item or Upuer Limit (DDm)

Substance of Special General

Bad odor Chemical Description District District

Ammonia NH3 Stimulation 5 1

Methyl melkaputhan CH3SH Putrefied Onion 0.01 0.002

Hydrate sulfate H2S Putrefied egg 0.2 0.02

Methyl sulfate (CH3)2S Putrefied onion 0.2 0.01

Tri-methyl ami (CH3)2N Putrefied fish 0.07 0.005

Methy di-sulfate (CH3)4S2 Putrefied onion,

stimulation 0.1 0.009

Acetaldehyde CH3CHO Stimulation,

boiling point 21° C 0.5 0.05

Styrene O-CH - CH2 Stimulation 2 0.4

The hydrated metal produced through the above process has a rather low

solubility, so that the density of toxic metal ions in the liquid phase decreases considerably.

The reduction of the leaching of toxic substances is achieved through

the above two mechanisms, i.e., the chemical fixing effect by Ca2+ and the

hydration and sedimentation effect by OHFigure 6 evaluates the reduction ratio of leaching of heavy metals by

lime treatment, which was carried out by Bechtel Company. According to this

figure, most of heavy metal ions are removed and become harmless by the production of calcium salts and hydroxide. Only Cr6+ ion shows a low value of

the reduction ratio.

In the case of utilization of bottom sediments in residential and public

areas, standard or limit values for soil pollution, as published by the

Japanese and local governments, may be applied (see Table 4).

232
100

C)

0 50

(D g s a d C C C fg hin Ni Pb -Z

Figure 6. Reduction ratio of leaching of heavy metals by

lime tre3tment

METHODS FOR SOLIDIFICATION OF BOTTOM SEDIMENTS

Methods for solidification of bottom sediments are basically classified

into two types, described below.

In Situ Solidification Ty~e

In situ solidification is applied at the following areas (as shown in

Figure 7):

a. Disposal area for dredged bottom sediment.

b. Lake, sea, and river where bottom sediments deposit.

_q. Very soft ground necessary for shallow ground improvement.

Process Treatment Tyge

Process treatment solidification is applied to the following areas (as

shown in Figure 8):

a. Bottom sediment on the way to disposal area after dredging.

~.Mud slurry produced at the site of shield works or in situ piling

works.

Solidifying plants or facilities are popularly used for the process

treatment type. Solidification methods are summarized in Table 5.

CONCLUSION

Properties of bottom sediments vary because of the different factors of

origin and development processes. Treatment of bottom sediment in the construction stage is closely related not only to the design codes and standards

233
0 : 00 : : 0 0 0 0 0 0 0

* 0 0 aI i 00 0

- , :: ,~ ,0 0 , , :

-JA F

l mi

I

0 0000e

)1 0

(23

C>

-0

P.2

a -aca ' 4 0
*xccu eurpose t ion

(1) Disposal Area for Dredged Sedimient L.Itrol live

oreler weivery riot Deep Trick *wlidoler

oll ic d b fi ll ill Lye r p / -

(2) Solidification at Lake. Sea & River

Lateral Type

" ..L z t '/ / / ] / I Y I l lc l i e

4to, lIlelo o. of Iooki. ,) (for EIt.islo. of leacholi)

(3) Shallow Improvement for Civil Works

n-Cven] r (foolto k iertical pt JType._ ,

~:-j[tllLiI a.,.

[(aot - - ootd-(t,-,o. log Cutecoti fr,4ot [to, Sookaull Slabiliter Type

Figure 7. In situ solidification type

for civil works but also to the environmental regulations for containing the

organic matters and toxic substances.

From the above point of view, the solidification technique for treatment

of bottom sediments in Japan has been reported in this paper. In summarizing

this paper, features of the solidification technique are shown in Figure 9.

235
(I) lottom Sediment on the Way to Disposal Area

Dredger

DeIi very

c =

I I

Permanent Plast Type Temporary Plant Type

Drelged Sediment

0:a S0 Chemicals Dredged Sediment

coca

Miin gn Ili ture --

Chemicals i 0* vMre r

M - trot Mixture

(2) ud Slurry from Shield Work or I-situ Pills# Work

(Un-sitA Piling Work) T -...d.s11 r ry

Chemicals -Ceii lu fiizinit Pit

Figure 8. Process treatment type

SOLIDIFICATION TECHNIQUE

- To be Workable on Mlud

Very Soft Soil - To Ensure the Required Strength ( - 100-300%)

To Enshort the Work Period

Toxic Soil * - To Keep the Environ mental Requlations

To Treat without Waste Water Disposal

Organic, So I - To Extend the Application

(Lig. =10-30X)

- To Enable the Economic Design

Figure 9. Features of solidification technique

236
TABLE 5. SUMMARY OF SOLIDIFICATION METHOD

In-itia Solidificatlon Solidification by Solidlication by

Lateral Type Stabilizer Type Verllcal Type Temporary Plant Permanent Plant

Use 14U1.*t (IS j) :aa I ICOX) J aISMlVt Is~ aa

OePth 10 " less thin 1.5. less than 3.0. 1.0. - 2.0.

[Chemicals Supply Centel Slurry Powder or Slurry Cement Slurry Cement Slurry or Powder Powder

Workability Workable o Mud Workable on MUd Workable on Mud by Sack floe

Operation Surry Plant Powder Feeder Slurry Plant Powder Feeder

Apoliability for lil-scale Work (or load Work for Small-scale work

237
DEVELOPMENT OF A VACUUM CONSOLIDATION METHOD

EMPLOYING HORIZONTAL DRAINS

AD-P00 6 467 T. Chiba, H., H. Shinsha, Y. Tani

Japan Dredging--Reclamation

Engineering Association

1-11-25 Higashi-Ohi, Shinagawa-ku

Tokyo 140, Japan

ABSTRACT

A vacuum consolidation method employing horizontal drains has been developed as a way to improve very

soft ground. In this method, plastic board drains are

laid in extremely soft ground with roughly 1.0-msquare arrangement, and a vacuum is applied to the

clayey soil from one end of the drain to consolidate

and improve the soil.

From this development project, the following

conclusions were reached:

a. According to laboratory experiments

conducted on vacuum consolidation, a

high level of improvement equivalent

to loading consolidation has been

obtained when a vacuum is applied to

clayey soil.

b. From the onsite experiments, it was

found to be relatively easy to lay

horizontal drains in the ground.

c. It was verified that soil in landfills produced by the disposal of

dredged clayey soil and in disposal

sites containing slurry can be significantly improved by this method.

INTRODUCTION

When land is reclaimed by disposing clayey soil dredged from the sea

bottom when deepening sea lanes or harbor facilities, or in waste disposal

sites where slurry discharged from chemical plants or other facilities is

stored, ground is created which is so soft it is difficult for a person to

walk on. The authors and their colleagues are engaged in the development of a

vacuum consolidation method employing horizontal drains as one way of consolidating such very soft soil in a short period (References 1-5). In this

method, plastic board drains, each having a square shape with sides approximately 1.0 m long, are laid horizontally in very soft soil, and vacuum is

applied to the clayey soil through one end of these drains to bring about

238 92-10787

92 4 404 2 ,l!!l J*lI~lllllmllll
consolidation and improvement of the soil. The reasons why the combination of

plastic board drain and vacuum consolidation was selected as the land improvement method were: (a) loading consolidation is difficult when the soil is

extremely soft, and vacuum consolidation is obviously ideally suited to the

situation; and (b) installation of drains was essential to reduce the consolidation time, and plastic board drains maintain their performance even in

extremely soft soil.

This method has the following characteristic advantages:

a. Extremely soft land can be settled substantially within a short

period. Thus, it is possible to dispose of 1.5 times as much clayey

soil on the same disposal site as compared to conventional methods.

b. As the very soft soil is improved by applying a vacuum, the strength

of the clayey soil is expected to increase even after the improvement

operation. Thus, it is easier to spread sand over the surface of the

land than with conventional methods.

The idea of improving very soft soil using horizontal drains has been

introdlced before. However, as there was no practical way to lay drains in

the soil horizontally, this idea did not materialize. With the drain laying

method introduced in this paper, drains can be laid in the soil very easily.

Basic laboratory experiments on vacuum consolidation are described

first, and then the performance in actual soil improvement tests conducted

onsite with laid drains is reported. The onsite experiments were conducted on

a landfill made by a pump-type dredging vessel, which disposed clayey soil

from the sea bottom, and in a disposal site for slurry.

BASIC LABORATORY EXPERIMENTS ON VACUUM CONSOLIDATION

One-dimensional consolidation experiments were carried out to identify the effect of vacuum consolidation on clayey soil. These experiments

were conducted in order to compare the performance of this method with loading

consolidation, and also to identify the effect of vacuum consolidation on the

improvement of clayey soil.

Experimental Method

The experimental setup is illustrated in Figure 1. The vacuum used for

consolidation was controlled by adjusting the pressure reading to specified

values on a mercury manometer. Loading consolidation was performed by air

pressure loading, and the experiments were conducted with 0.4 to 0.5-kgf/cm2

back pressure.

Samples used were clay taken from Tokyo Harbor with water content controlled at W. equals 110 percent. After the clay was disposed in the mold,

the pore pressure gauge was installed. The sample was placed in water between

the upper part of the sample, and the membrane was drawn out through the rubber tube. The pore pressure gauge was set at the specified position by cutting a hole in the side of the mold. The hold was then plugged with a rubber

plug to seal the sample. The experimental conditions are given in Table 1.

239
Mercury Vacuum Vacuum

Test- Dial Pore pressure gauge manometer regulator pump gauge,/ Tr , aomtreuao pump

Filer° paper

Test-i .Pore pressure guage.,

(2.5cm.itris) Test sytem by bacuum

-- Mold Back pressure

(Hl 10M) Air pressure

- U Cell

Test syten by air pressure

Figure 1. Experimental setup

TABLE 1. EXPERIMENTAL CONDITIONS

Test W (%) a (Kgf/cm2 )

-0.05, -0.1, -0.25, -0.4,

110 -0.8, 0.05, 0.1, 0.2,

0.4, 0.8

II 110 -0.8, 0.8

Comparison of One-Dimensional

Consolidation by Vacuum and Loading

Figures 2 and 3 show the results of the measurements made on settlement

and pore water pressure in Experiment I. When the settlement curves for

vacuum consolidation and loading consolidation are compared, both settlement

curves are found to be approximately in agreement until the average degree of

consolidation reaches 80 to 90 percent, under all loading conditions. When

considering the long-term settlement curve obtained with jaI equal to

0.8 kgf/cm2 , it is noted that the settlement proceeds linearly on logarithmic

coordinates. On the other hand, the measurement results on pore water pressure indicate that the process of dissipation of pore air pressure is exactly

the same as the process of propagation of vacuum.

240
Elapsed time. t (min)

0 10 , i ,III I, 10 1 1 1 1 1 111,, 10

1 --' - I .1kg Vc'n'

I~ ~ ~ ~ ~ -;'*W."-::-: --~~~0 ,.-- .;= .5

10

01 t___"____ "s Ela. ;+ m. (-)

I-" ;o.' 'N 10' .- _ --__ __ \ ;-0' 00 0 0

0 0.1-0

S eO - ji 8 o0

Figure 2. Settlement curves (Experiment I)

2 003 0 1 Elapsed time. t (mi) _ 1W' 10, 1W

00 0. 2 0. 06

0.014 11 0.0 -0--

0 Io.. o 8 -0.1 - 02

L 0051 01 -- 05 '04 08

Figure 3. Pore water pressure measurements (Experiment i)

The measurements on settlement and pore water pressure in Experiment II

are given in Figure 4. In this figure, the settlement curves for vacuum consolidation and loading consolidation are in very good agreement, and the

trends in the pore water pressure are also in fairly good agreement. When

examining the measurements on pore water pressure for vacuum consolidation in

Experiment II, it is found that the pore water pressure in clay decreases to u equals -0.6 kgf/cm2 , but then tends to rise when this pressure is reached.

The reason is probably because the vacuum causes the dissolved air in the pore

water to expand.

241
Elapsed time. t(min)

A 100.

400

"_ " . 0.3

Figure 4. Settlement and pore water pressure measurement

(Experimental I!)

The results for water content after completion of vacuum consolidation

and loading consolidation are given in Figure 5. It is apparent from this

figure that the water content and density after consolidation are exactly the

same for both methods.

From the above experimental results, it can be concluded that onedimensional consolidation by vacuum and by loading are identical processes.

On the actual site, real improvement can be expected using a vacuum in

the range of -0.5 to -0.8 kgf/cm2 when applying vacuum consolidation to horizontal drains. For example, the water content after consolidation is

W - 65 percent in Figure 5, and a substantial reduction in volume can be expected when a vacuum is applied to clayey soil.

i IMPROVEMENT OF SOIL IN A LANDFILL MADE BY DISPOSAL OF CIAYEY SOIL

DREDGED FROM THE SEA BOTTOM

An onsite experiment with the vacuum consolidation method and horizontal

drains was performed in a landfill in Oita Prefecture. This land is extremely

soft dredged soil which has been standing for approximately half a year after

disposal. In this experiment, 40 drains were laid in the soil, and a vacuum

was applied until consolidation was completed.

Outline of Experiment

The plan of the experiment site is shown in Figure 6.

242
90

" 70

60

0.05 0.1 0.2 .0.4 0.8

Consolidation pressure. atkgfc?)

1.7

1.6

600

1 1 i g ui 1 I I I II 0.05 0.1 0.2 0.4 0.8

Consolidation pressure. :;(kgf/cd)

Figure 5. Water content and density after

consolidation

The soil improvement area is located approximately 30 m inside the landfill from the central bulkhead. Here, 40 drains (in four levels and 10 rows),

each 50 m long, were laid horizontally with 0.7-in horizontal and vertical

spacing. The depths of drains were, as indicated in Figure 7, G.L. -1.0 m for

the uppermost level, and the surface layer of soil in the improvement area,

65 cm in thickness, was left out of the improvement zone. The surface soil

was left out because it was expected that this layer would provide a sealing

effect against the vacuum. The drains are the same as those used for conventional vertical drains, with a 10-cm cross section and 3-cm wall thickness.

The vacuum was applied continuously for 57 days, and the data -"own in Table 2

were collected continuously over this period.

Drain Laying Method

The horizontal drain laying system is illustrated in Figure 8. The

drain laying system consists of a polystyrene foam barge carrying the drains

and the gear which guides the drains to the specified depth. The drains were

laid in the sequence below.

a. With the guide gear fastened to the barge, the drains and drain hoses

with caps are connected together. The drain hoses were connected to

the anchor pile.

243
Experiment ar'ea

50in Survey bare

ICentral bulkhead -61 hose o 

I t Vacuum pump room 50inI S~in Measurment hut

513.3 6.7.6.7 13.3 51

HIlorizontal dralini j Landfill

jimprovement area

~'J7 ~ 4 + Settlement and horizonta!

Vertical drain displacement measurment bores dil 10(a total of 13)

Figure 6. Plan of experiment site

7 in

L(3

,2 0-

I1 Improvement

I zone

--------------------- 1,.-3.I1m

Plastic board drain A; Pore pressure

0.111 intervals. 50m long. 40 drains ) R3Uge

Figure 7. Cross section of installed horizontal

drain

244
TABLE 2. MEASURED DATA

Measurement

Measured Data Point Measurement Method

0 Drain amount 1 Cumulative flow meter

0 Working vacuum 1 Pore pressure gauge

* Pore water pressure 6 Pore pressure gauge

inside drain

* Settlement 4 Level survey meter

* Horizontal displacement 4 Transit survey

7m

SWinchi@;0 Drain

f orce farge (3 5 x i ra)

EPolystyreiie foam ' ~MI ri ose

- " Anchior

(; ide gear Rol ler

Extremely soft ground

Figure 8. Horizontal drain laying system

. The guide gear was driven into the clayey soil by a winch, and at the

same time the anchor pole was pushed into the soil. When the guide

gear reached the specified angle (45 deg), the guide gear drive was

stopped.

c. With th- guide gear buried in the soil, the barge was winched towards

the bv-ial point, laying the drains as it moved.

d. The barge was stopped temporarily at a point where the 45-m sections

of drains were laid, the drains were cut to the specified lengths,

and the drain ends were sealed.

e. The barge was again driven in the direction of burial, to complete

the laying operation.

One row (four drains) of drains were laid in a single operation, and the

operation was repeated 10 times. As the draft of the polystyrene foam barge

245
was 10 cm, and the water level was 30 cm above the soil surface, the barge was

completely afloat. The traction force was approximately 300 kg while the

drains were being laid, and the laying operation was not difficult as the

ground was extremely soft.

Vacuum Loading System

The vacuum loading system is illustrated in Figure 9.

Static strain gauge Fuel tank _ I ON/,Fale_

Fuel tank. Switch board O

Generator raii iose ... ................. ...i

Flow meter IVacuum Pore j4 's6i'gauge

Electrode Itransduce es e a

I _A

Drai pum Drainc

50m

Sump tank Vacuum tank 50Morizontal

Horzonaldrain divider

I Vacuum ~150/ OOLpump __

/ mi

n) I :"..

-LIL- - -.- -J

Internal 24 drains

Figure 9. Vacuum loading system

The drain passed through the suction head, and then to the vacuum tank.

There was a drain -ump in the vacuum tank, which was activated when the water

level reaches the upper electrode, automatically draining the water to the

sump tank. In route, the drain water passed through the flow meter, and the

cumulative flow was recorded.

Experimental Results and Evaluation

Vacuum Versus Drain Speed

The time variations in the vacuum level in the proximity of the vacuum

pump, the cumulative volume of drain water, and the drain speed are illustrated in Figure 10. It can be seen from Figure 10 that at first a high

vacuum of -0.9 kgf/cm2 was maintained, which decreased with time, reaching

-0.75 kgf/cm 2 at t equals 57 days, on which day the experiment was terminated. The reason for this decrease was the rise in Lemperature of the vacuum

pump cooling water, which reduced the pump suction efficiency.

The cumulative volume of drain water was 510 m3 at t equals 57 days.

The drain speed for all 40 drains (q) was q - 40 I/min immediately after the

vacuum was applied, but decreased as consolidation progressed and fell to

246
Elapsed time ;t(day) 0.1 0.5 1 5 10 50

(I I I |1 I'111 I ' II "I ; I I I i i

=-0.8-

C-0-0.6

S0

10- I

20 - 2 "S

-- I I a 

30- ,o =

40 - -e\,

50- I

60 I -I 6 x10'

Figure 10. Vacuum, cumulative drain volume, and drain speed

approximately one half the initial value after I day. At t - 57 days when

the experiment was completed, q equaled 3 I/min, exhibiting a drastic

decrease.

Variation in the Water Content

Variation in the water content with time at the center of the improvement zone is illustrated in Figure 11. A preliminary survey before the experiment indicated that the water content at the surface layer was w - 200 to

300 percent decreasing gradually as the depth increased. This decrease can

be accounted for by the larger sand content with depth and the process of

consolidation under the weight of the soil itself.

The data at t - 20 days indicated that the improvement zune was mixed,

with areas where the water content had decreased to around 90 percent, and

some areas were still as high as 150 percent. This indicated that the water

content decreased near the drains but still was high in areas between the

drains, and that consolidation was still going on at t - 20 days. At

t - 40 days, the variation in water content almost disappeared, and the water

content was almost uniformly distributed at 90 to 100 percent everywhere at

t - 57 days.

When the drain depths were studied at t = 57 days, it was found that

the first-level drains had sunk approximately 1.3 m from the initial laying

depth. The distance between drains was approximately 60 cm between the first

level and the second level, and approximately 40 cm between the second level

and the third level and also between the third and fourth. In vacuum

247
Water content w(%) Sand content Ms(%)

0t10 200 300 o to 20 30

T=7

a. Point A

Water content w(%) Sand content Ms(%)

0100 200 300 0 tO 20 30

+ 0 1-0Y/

57

b. Point B

Water content w(N) Sand content Ms(%)

+5 too 200 300 0 tO 20 30

+5 / ToT 7 7

20 4o days

T=57 days - 0

'j+3 dra in 0

10 C

o t_ 0 57

- iio

C. Point C

Figure 11. Variation in water content with time

248
consolidation, the vacuum causes the clay to concentrate around the drains.

This tendency caused the clay in the surface layer to move to the periphery of

the first level, allowing the second level to drain. As a result, the

interdrain distance at this level decreased by only 10 cm.

The water content was w - 90 percent or so in the layer between the

soil surface an the first-level drain, and the water content increased almost

linearly as the depth decreased. The first-level drains were laid at a depth

of G.L. b - 1.0 m initially, but this depth changed to G.L. - -1.3 m after

t - 57 days. The reason that the thickness of the surface soil increased was

that the clay from the surrounding areas flowed into the upper layer of the

improvement zones.

Settlement Curve

The settlement curve is given in Figure 12. This figure indicates that

there was no difference in settlement at the proximity of the drain hose and

at the tip of the drain.

Elapsed time t(day)

5 10 50 04 1 1 I I I I I I I I

40- 3

.:4

,, 60

808

50m If

100 1 5 13.3 13.3 13.3 511

14 13 12 1 A

120- 44i.-

140

Figure 12. Settlement curve

By assuming that the initial water content of the clay before improvement was wo - 200 percent, and obtaining the consolidation strain ef by the

following equation, the result is ef - 44 percent.

- - ef f= + e°

where

Initial void ratio: eo - G. x w. * 5.3

ef k 2.5 wf k 94%

(specific gravity, G, - 2.65)

249
In considering the consolidation speed of extremely soft clayey soil,

the change in layer thickness cannot be neglected as the consolidation process

is accompanied by a large strain. Here, Barron's consolidation theory was

applied as an approximation of the consolidation process with horizontal

drains, and the effect examined. The result is indicated in Figure 13. In

this figure, the measured consolidation curve approaches the theoretical curve

with drain distance d.. - 70 cm at the final stage of consolidation and the

curve of d,0 - 40 cm at the final stage of consolidation. If the consolidation speed is proportional to the square of the layer thickness, the theoretical drain distance can be obtained by the following equation:

= [(d0 o2 + d f2)/2] 1/2

When the theoretical curve is plotted in the same figure, the curve

shown by the broken line is obtained. When this theoretical curve is compared

with the measured curve, they are found to be in good agreement on the average. Then it can be concluded that the method based on Barron's consolidation

theory is applicable to the actual consolidation process with horizontal

drains.

Elapsed time ;t(day)

1 5 10 50

o 0

N0

500

oo

Figure 13. Comparison of measured versus

theoretical curves

The results of unconfined compression tests on the soil after consolidation are presented in Figure 14. The average strength after improvement was

- 0.125 kgf/cm2 .

IMPROVEMENT OF WASTE DISPOSAL SITE FOR SLURRY

A project was conducted to improve the soil at a waste disposal site for

slurry (soda ash) in Yamaguchi Prefecture.

250
Unconfined compressive strength,.

o q "(kgf/cn) 2 +51-"

+4 /////-

-+3 Horizontal _ drain

+2 - so •

CID

+- I **

0.

-1

Point B( center)

Figure 14. Unconfined compressive

strength after

improvement

Outline of Improvement Project

The site where the improvement project was carried out is illustrated in

Figure 15. The total improvement area was about 40,000 m2 . The drains were

laid in three levels and in square cross sections, which were each separated

by a distance of 1.5 m. The total length of the drains laid amounted to

approximately 80,000 m. Three types of drains were used: 10 cm wide x 3 mm

thick, 10 cm wide x 6 mm thick, and 15 cm wide x 12 mm thick. In this project, improvement was performed with surface water present all the time.

Initial Soil Condition

and Soil Characteristics

The soil characteristics of the soda ash layer before improvement are

presented in Figure 16. The water content was 500 to 600 percent at the surface, decreasing with depth. Electrical cone penetration tests were conducted, and it was found that the penetration resistance at the surface was

very low. According to the consolidation tests in soda ash, the coefficient

of consolidation in the normal consolidation zone was C, - 500 cm2/day, and

the coefficient of volume compressibility M, - 0.2 p-0. 92 cm2/kgf (p - effective stress).

Method of Laying Drains

The drains were laid by an improved type of laying barge. The drain

laying procedure was the same as described in Figure 8.

The laying procedure is illustrated in Figure 17. Winches were installed on the banks on both sides to pull the laying barge forward and backward. A bulldozer was stationed on the line of laying and was used as an

251
Pore Pressure

Vaumgup; 1auge Vacuum Pump

uuaive flow meter

Settlment orraDrain laying Setlemntbo d~al ....... (lO0mx3mm. 1.5m separation)

Section 2 -Settlement "

Drain laying board

(loom. X 3m. .5m %1 se~artin\ Drain laying (10Sem.1 1 5 earation .)

Drain laying *board,%8

(l5Omm X12mIJ Unimproved arean K~I5m separation / I1

~ ettlement board No.*1

Pore .pressure gauge No.4

L~rf Section3

Section I Drain laying

The arrows indicate I.he Drain laying AZA.959mn xl2mm 1. 5m separation)

direction of drain laying (100mm X3mm. 1.5m separation)

in each section.

PJ~~ Vacuum pump

Figure 15. Project plan for improvement of waste

disposal site for slurry

SCone penetratior Particle (96) Specific 0 Cnitny0 7= ~ resistance 0 size weight G3 ossec

CZ kfcn) cmpsto 2.6 12.7 Natural Coefficient

00 0.1 0.9. . watercontent(%) 0 of

rt g./cmn) Liquid I mlt (%) 0 compression

GH - Unconfined 01.11.3 1.5

*~compression q Clay Silt LL Plastic Ilimit(*%) An Cc

(M) Void r a tio0a

.02. 04 .06. 08 25 50 75 5 e 10 100 200 300400 500 1 3 5 .... ... ...

2 - 0 /-2.80

CO 0

4.00 0

Figur 16. Soil haraterisics f.sod.ashlaye

252....
Anchor point bulldozerl)60P

0 1 ocl Lse receiver

3 t -W i n c hI

Wire rope_\, Laying barge

for pulling back 16 'A Laser receiver

For barge steering

Landfill

Guide rope

Buoy (techniron. floating)

022

f r e\\ Laser beam

Block for bearing correction

Wire rope for laying 016

Wareouse aser transmitter

Siteo eAnchor point bulldozer

3t Block 3t

3t

Figure 17. Barge operation

anchor point. This bulldozer also helped to improve the operational efficiency of the drain laying. As a guide to allow drains to be laid on a

straight line, a floating rope was strung parallel to the direction of laying,

and the laying barge moved along this rope.

Experimental Results and Evaluation

Relation Between Soil Strength

and Traction Force of Barge

The relation between the cohesion of the soil and the traction required

to lay the drains is illustrated in Figure 18. The following relation between

the cohesion C and the traction force T had been obtained.

T = 4.OC + 0.5 (T: tf, C: tf/m)

This cohesion force has been obtained by the relation c = q,/10 from

the cone penetration resistance tests.

253
lOcaX 3m. Ldrain mandrel :0

~I5cmnxI2mmu 0

urain mandrel

84

UI - - f

00o

Coeso foc-o4oi-.t/d

Cohesacion force of olayingrd

barge

Drain Laying Time

The time spent is laying drains of 10 cm wide x 3 mm thick for lengths

of approximately 100 m are illustrated in Figure 19. The time required to lay

a single row of drains was approximately 32 min.

Frequency

41(38 (probability as

10 ODrain Laying leagili

Sect ion 1. 2. and 4 100,

o QAverage time

~30- Ca

05

043

10-

0020 25 30 35 40 45 50- 55 (i0over

Cycle time TWOri

Figure 19. Drain laying time

254
Measurement of Settlement

and Volume of Drain Water

The time variations in the working vacuum, settlement, volume of drain

water, drain speed, and pore water pressure in Section 3 of the plan area

(Figure 15) are illustrated in Figure 20. Drains that were 15 cm wide x 12 mm

thick were laid in approximately 200-m lengths. According to the data on

settlement in Figure 20, there was little delay in settlement between No. 11

point, which was the nearest to the pump, and No. 7 point, which was the

farthest, indicating that the whole area of Section 3 settled uniformly.

0.1 1 10 100

=-0.5. \ pore pressure Sect t \ gauge Ne. 4

n Vacuum applied

C _

S-15........... ".... .............. ~olcvrn

00

=- o ; k No. 8

100

-0.5 i~ No. 7 = NO.Nl. 9

le ll w ot=41days ,o \Start of primary

-1.5l Loadg oncovering O, 0

200 5000

Crdrin wate

400 drain atr, l000

6 W C. (i ,, of.a 10 [100 15000 i

Loadin on Loading on Elapsed time

lowest level lower two t (ay) levels Loading on

all levels

Figure 20. Measurement of settlement and volume of

drain water

When the volume of drain water was observed, the total volume was

approximately V, - 8,000 m 3 at the time when settlement reached approximately I m. On the other hand, when the empty space created by spttlement was

r q 1 ,,! 11 :a f-- , 1, - nnn m3 (size of an area 15 m in width x 200 m in length X

l-m decrease in height). Therefore, the seepage of water from the soil surface was 5,000 m 3 , which was considerably larger than the water squeezed out

of the soil, probably because the soil surface was dry and there were invisible cracks. The fact that settlement proceeded uniformly despite the large

255
amount of seepage water indicates that the drain capacity of the 15-cm-wide x

12-mm-thick drain material was sufficient even with the presence of a large

amount of surface water.

Considering the variation in drain speed with time, the drain speed immediately increased when the vacuum was applied to the drains and then gradually decreased with the consolidation time.

Selection Through Drain Material

The volume of drain water passed by each type of drain is presented in

Table 3. The time of 30 days in the table is the time required for the average degree of consolidation to reach approximately 80 percent. The average

volume of water drained per one drain per day can be calculated from the following equation:

q = Q/(t x n)

where Q is the volume of water drained in 30 days, t is 30 days, and n

is the number of drains.

TABLE 3. MEASUREMENT OF DRAIN CAPACITY

Type and inmher Emipty cross section Volume diained % nverge flow Studied by Symbol of drain material of drain material after 30days for 30 days Project

-1 s Q q=Q/(tn) Section

" lOcinwidex3inmtlhick I cnf 700 nf 1.14 Section I

204drain. IOOmlong n?/day/drain

o lOcmwidexGmnthcl 5 cn? 11. 000 n? 2.26 Section 4

20'drain. l00uulolR n?/day/drain

A 15cnmwideXl2mmtlihck 12 cnf 8.000 n? 8.89 Section 3

30d ra in. 200 I log rf/day/dra in

Li I0cmwidex3imnlliick I cnf 370 11? 0.31 Oi ta

I 40diaiu. 50,nlong I m'/day/drain Experiment

The relation between the average drain capacity and the empty cross section of the drain material is summarized in Figure 21.

It can be seen from this figure that the maximum drainage capacity increases rapidly with the empty cross section. Therefore, when an attempt is

made to improve clayey oil by applying a vacuum, drain material must be

selected so that the designed drain capacity is on the right side of the

broken line in Figure 21.

256
10 Synilo l S Q

-~1 ~/ 1. 14

"E 0 5 2.26

/ 12 8.89 / ~/

Z 5- 1 0.31 7

-o -

01.0

1 5

Empty cioss section of diain material. S (cm')

Figure 21. Relation between empty cross

section of drain material

and average drain capacity

Soil Improvement Performance

. Change in water content, Typical changes in the water content are

illustrated in Figure 22. The water concent was wo - 500 to

600 percent at the soil surface and 300 to 400 percent below the

-4-m depth before improvement. In contrast, by the time settlement

had reached 85 m (but not completed), w - 400 percent at the surface and 200 to 300 percent at depths below -4 m, indicating a marked

reduction in the water content after consolidation.

h. Penetration resistance, Results of cone penetration tests conducted

before and after soil improvement are presented in Figure 23. The

tests after improvement indicated that there remained a layer having

a penetration resistance of q, < 0.05 kgf/cm 2 from the soil surface

to a depth of around 1.0 m, while qc - 0.5 kgf/cm 2 was obtained in

the improved soil. The reason that a low resistance layer remained

near the surface was that water seeped from the surface to the drain,

as the soil surface was not sealed by sheets.

CONCLUSIONS

In this report, the vacuum consolidation method employing horizontal

drains has been discussed as a means of improving very soft soil. The conclusions reached are as follows:

a. When a vacuum of around -0.5 kgf/cmn2 was applied to clay in Tokyo

Harbor, the water content was reduced to approximately 65 percent.

Based on this performance, it was concluded that the vacuum consolidation method has a substantial effect in reducing the volume of very

soft clayey soil.

257
Original soil Water content w(%)

200 400 600 800

't 85cm settlement (2 0 Dain

Drain 00an

-20 0 e O 0 Diain

*00

~-3Drain, 0* 0 C 0

0 0( -30 _ 0. tiailO

Drain, 0 (9 _ 0 o0 0o Legend

-5 I () efore Improvement

At 85cm Settlement

I _ _ _ II

Figure 22. Change in water content distribution

Cone penetration resistance. q,(kgf/cd)

0 0.5 1.0

Original soil

0 ,

0 o Soil improvement surface after E

-1IL

-000 0 :Before soil

-2 0 improvement

.C 0 0 *:After soil

0 * improvement

0

-3 0 0 0

0

0

-4 0

0 0 0 -

0 0

-5- 0

0

E)

Figure 23. Distribution of penetration resistance before

and after improvement

258
b. It was verified by experiment that laying horizontal drains in soil

is relatively easy.

C. The experiment conducted on a landfill made of dredged clayey soil

indicated that the initial water content of w - 200 to 300 percent

in clay was reduced uniformly to 90 to 100 percent after improvement.

The average soil strength after improvement was q,, - 0.125 kgf/cm2 .

d. The experiment conducted on a waste disposal site for slurry indicated that (1) application of a vacuum through 15-cm-wide x 12-mmthick drains laid for approximately 200 m resulted in uniform

settlement of the improvement area, and *2) the water content measured before improvement was 300 to 600 percent but was reduced to

200 to 400 percent after improvement.

At the site, experiments were conducted with surface water over the

soil. A low-strength, clayey soil layer remained from the soil surface to a

depth of approximately 1.0 m. It is necessary to develop a method by which

the surface layer can also be improved.

REFERENCES

1. "Experiments on Land Relating to a Vacuum Consolidation Methud Employing

Plastic Drains," Ground Engineering, Vol 2, No. 1, pp 33-40, 1984.

2. "Improvement of Reclaimed Cohesive Soil by Vacuum Consolidation," International Symposium on Geotex., pp 125-133, 1987.

3. "Research in Vacuum Consolidation Method Employing Horizontal Drains,"

Part 1, 22nd Symposium of Geological Engineering Research, pp 1783-1784,

1987.

4. "Research in Vacuum Consolidation Method Employing Horizontal Drains,"

Part 2, 22nd Symposium of Geological Engineering Research, pp 1785-1788,

1987.

5. "Research in Vacuum Consolidation Method Employing Horizontal Drains,"

Part 3, 23rd Syposium of Geological Engineering Research, pp 2129-2138,

1988.

259
TOXICOLOGICAL ASSESSMENT OF HAZARDOUS WASTES

S. A. Peterson

SD-P006 468 US Environmental Protection Agency

Office of Research and Development

]IllJJ] 11111 fII 11NIl III I flII]]W Seattle, Washington 98112

ABSTRACT

Section 121 of the Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (SUPERFUND) calls for

hazardous waste site remediations which permanently and

significantly reduce the volume, toxicity, or mobility of

hazardous substances, pollutants, and contaminants. Traditional engineering technology has concentrated on reduction

in volume and mobility as assessed by chemical and geophysical measures. It was assumed that accomplishment of

volume and mobility reduction would lead to reductions in

toxicity. Environmental scientists long have argued that

this assumption might not be the case. However, lack of consensus on how complex hazardous waste mixtures should be

measured toxicologically hampered integrated assessments.

Therefore, a battery of aquatic and terrestrial bioassays was

assembled and evaluated comparatively against several chemicals and waste site chemical mixtures. The bioassays were

then applied to a mobility reduction demonstration to assess

its overall chemical, physical, and biological performa,ce.

Results indicated that, while the primary objective of

mobility reduction seemed to be achieved, undesirable secondary effects (toxicity) were introduced. These trade-offs

must be considered in the holistic sense when remediation

measures are being implemented.

INTRODUCTION

Legislation

Public concern for environmental and public health effects resulting

from the disposal of industrial and agricultural waste mixtures led to the

development and passage of the Comprehensive Environmental Response, Compensation, and Liability Act of 1980. The purpose of this'act, commonly known as

SUPERFUND, is to remediate hazardous waste sites in ways that permanently and

significantly reduce the volume, toxicity, or mobility of hazardous substances, pollutants, and contaminants.

92-10788

02 4 24 222
Traditional Approaches

Chemical Measures

The traditional approach to the hazardous waste site problem assessment

has been to make a series of chemical analyses for priority pollutants (129

consent decree chemicals) and apply these concentrations against existing

chemical criteria or standards (Keith and Telliard 1979). The individual

chemical exceedances might then be taken collectively to assess relative risks

at a site. A major concern with this approach is that the priority pollutant

list consists primarily of human health carcinogens and mutagens, i.e.,

long-term bioaccumulating chemical effects rather than short-term toxic

effects.

Shortcomings

Because of the above approach, ecological considerations are minimized

relative to human health concerns. Other shortcomings to the chemical-bychemical criteria assessment approach include:

* Inadequate databases for developing sound criteria for many

chemicals.

Lack of criteria values for many chemicals encountered at hazardous

waste sites.

a Criteria based on laboratory studies underprotect or overprotect when

applied to the field.

* Most criteria numbers give only limited consid-ration to environmental variability.

* Criteria numbers were not meant to be used additively.

* Soil and sediment criteria have been slow to develop.

Figure 1 illustrates the difficulty in estimating environmental toxicity

based on chemical analysis of site samples. The figure represents a typical

CC/MS scan of a waste site sediment leachate in which four priority pollutants

and nine nonpriority pollutants can be identified. Fourteen other organic

substances remain as "unknowns." Among the four identifiable priority pollutants, an environmental criterion exists only for phenol (3.4 mg/1). Thus, the

determination of environmental toxicity of this sample based on its chemistry

is nearly impossible.

Advantages of Bioassays

Ore way to offset problems associated with the use of chemical measures

alone is to supplement them with environmental toxicology tests (bioassays).

These tests provide a more direct measure of environmentally relevant toxicity

(Roop and Hunsaker 1985). Additional advantages of these test are that they

* Integrate the effects of all environmental variables and chemicals.

261
100_

786 EPA Pdodty Pollutants = 4

Non-Pdority Pollutants = 9

Unidentified Pollutants = 14

75 1839

50sosL

RIC 387

1176

474 18 835 ja 2 1

25 M6 1924

Scan Time 500 1000 1&00 2000 16:40 25:00 33:20

Figure 1. A CC/MS scan of a sediment leachate from the Western

Processing Site (Kent, Washington) showing peaks

for priority and nonpriority organic pollutants

* Provide a means of screening a wide variety of samples for acute

toxicity.

* Help identify media and organisms at greatest risk.

* Offer a means of directing chemical analyses.

This is not to say that short-term bioassays are without limitations.

Among the limitations are that they do not provide bioaccumulation factors;

they do not identify carcinogenic, mutagenic, or teratogenic effects; and they

are not chemical specific and thus cannot replace chemical analyses per se.

The advantages tend to outweigh disadvantages, but lack of consensus on which

tests to use and how to apply them has hindered their general application.

Therefore, an acceptable approach had to be developed.

APPROACH

Selection of Tests

Figure 2 shows a schematic diagram of the overall (single chtmical

through site application) approach to the problem. Initially, the need was

identified for a rapid, off-the-shelf method to assess relative toxicity of

complex waste mixtures at hazardous waste sites. A technical group met to

262
Lab Field

Multi Media Field

Develop Prtoo am._Cncept

Relative to

Bloassys

Assays of Assays of Bloassay of

Single chemical Comlex

Test It~e niomes Saf~i 

water, soil,

ent, Soil

I.achates

Comparative Comparative Comparaie Biological Chemical

AnalyzeoTo to Toxicology to Toxicology of Assmn l Aaye

chemicals Chemical Samples mixes

ComparativeVeicaonf

Analysis of Eooia

Results eso

Revised

Guidance on Apply Bo n

Remnedlation

Projects

Figure 2. Schematic uf the approach
discuss the tests that would most likely serve this need. Test species were

selected on the basis of available data, chemical sensitivity, ease of laboratory culture, and types of organisms representing various compartments of the

ecosystem. The tests selected included seed germination/root elongation (lettuce, Lactuca sativa L.), earthworms (Eisenia andrei), algae (Selenastrum

capricornutum). daphnia (Daphnia magna), fathead minnow (Pimephal.:s ;romelas),

and Microtox (Photobacterium phoshoreum). The latter test is a commercial one

(Beckman Instruments, Inc. 1982), but mention of this or any other commercial

product names does not constitute endorsement by the US Environmental Protection Agency. The test battery was designed to screen for relative acute and

short-term chronic (Algae Test) toxicity in surface water, groundwater, soil,

and sediment elutriate.

Danials (1981) and Peterson et al. (1989) have shown that sodium acetate

and acetic acid extractants increase sample toxicity. Thereforo, it was determined that soil elutriates should be prepared using deionized water. Water

was chosen as a conservative, natural leach medium that introduced no additional toxicity to the sample. The pH of deionized water is near neutrality,

thus approximating that of nonacidic rainfall. Soil samples were seived

through 0.25-in. hardware cloth prior to eluting. Water as well as soil and

soil/sediment eluates were adjusted, when necessary, according to Miller

et al. (1978) and Greene (unpublished data, 1984, USEPA) to comply with the

test organisms' known pH tolerances. Soil eluates were prepared by mixing

1.0 kg of solid waste (soil) sample with 4.0 2 of deionized water. The mixtures, each contained in a 10-1 cubitainer, were shaken at 100 rpm for 24 hr

at a temperature of 240 ± 20 C (later modified so the soil mixture was placed

into 1,500-ml glass vessels placed in a rotary extractor and mixed end-overend at 30 rpm for 48 hr). The waste/water mixtures were then centrifuged in

300-ml polycarbonate bottles for 10 min at 10,000 rpm and filtered through

0.45-,p membrane filters prior to assay.

While it is recognized that sample manipulation of this type will compromise absolute toxicity (usually reduces toxicity with metals as pH is adjusted upward, but less clear with organics), our primary objective was to

assess the relative, comparative toxicity to different test organisms across a

broad spectrum of waste types. Thus, all test organisms were exposed to sample material that had been prepared in exactly the same way. Fathead minnow

tests were conducted on only a limited number of samples. The procedures

described above constituted the "Protocol for Bioassessment of Hazardous Waste

Sites" (Porcella 1983). The protocol was subsequently tested against single

chemicals, mixtures of chemicals, and actual waste site samples containing

various combinations of chemicals. The purpose was to make recommendations

concerning the appropriateness of specific test types and to revise the test

protocols.

Comparative Toxicology

The graded comparative toxicological assessments allowed us to determine

how tests performed with various groups of chemicals, to establish the relative sensitivity of each test species, and to provide a logical sense of confidence that the test battery would detect a broad spectrum of contaminants

under varying conditions. Thus, when it came to actual complex hazardous

waste site toxicity, we could be reasonably sure that the test battery

264
responses were true indications of the relative, integrated (all chemicals and

environmental variables) environmental toxicity.

The EC50 or LC50 toxicities were reported as a percentage of the parent

sample material (water, soil, sediment elutriate). Thus, the lower the

EC50/LC5 0 , the greater the toxicity of the sample.

Application to Remediation Measures

The bioassessment protocol was used to help evaluate the environmental

effects of three soil stabilization and one vitrification procedure at the

Western Processing Site near Kent, Washington. The untreated soil and stabilized products were subjected to a series of physical, biological, and chemical performance tests. The commercial treatment procedures are proprietary so

the chemical formulation or composition is not revealed. Therefore, the only

way to know their composition was to chemically characterize them. The only

reasonably way to know whether they exhibited potential environmental toxicity

was to conduct bioassays. Experience with the above factors would eventually

be used to revise the "1983 Bioassessment Protocol."

RESULTS AND DISCUSSION

Miller et al. (1985) reported the results of single chemical, complex

chemical mixture, and hazardous waste site sample exposure of test organisms

in the Porcella (1983) "Protocol for Bioassessment of Hazardous Waste Sites."

The EC50/LC5 0 response values for each of the chemicals investigated were calculated by linear regression analysis of dose/response date. Specific EC5 0

chemical concentrations were reported as average values obtained from replicate tests conducted with each test organism. Results are summarized below.

Single Chemicals

Tests were conducted with the metals copper, cadmium, and zinc. The

individual chemical test results are aggregated in Table 1 to demonstrate

their relative toxicity and rank ordering among organisms of the Test Protocol. Algae and Daphnia were the most sensitive to these metals. They were

followed in descending order by Microtox, seed germination, and earthworms.

Two herbicides, 2,4-D acid, and Esteron 99 (a commercial formulation

2,4-D acid), were tested. Aggregates of the EC50 responses were obtained for

seed germination/root elongation tests at less than 0.17 mg/e (Table 2).

Algae, however, were more than 300 times less senisiLive than the seed germination test. This is most likely due to the fact that 2,4-D is an auxin analog,

which stimulates destructive growth in higher plants. Algae do not have auxin

growth regulation, but react to inhibition of the photosynthesis energy transport process. Thus, the difference in response between the seed germination

and algae tests is both biologically plausible and predictable. The seed

germination and algae responses were followed in descending order by Microtox,

Daphnia, and earthworms. Thus, the rank order of sensitivity for herbicides

differs markedly from that of the metals. It appears that one might eventually gain insight to the kind of contaminant that is responsible for producing

a given toxicity when a test battery of organisms is used. That information

might help direct chemical analysis where toxicity is deemed a problem.

265
TABLE 1. EC50 TOXICITY VALUES FOR HEAVY METALS*

Test Organism EC50** SDt CVtt Nt

Algae 0.042 0.005 12 12

Daphnia 0.22 0.04 20 12

Microtox, 30 min 4.98 1.24 25 20

Seed germination 69.93 13.59 20 15

Earthwormtt 623.90 124.80 20 9

* Modified from Miller et al. (1985).

•* Effective concentration at which 50 percent of organisms are affected.

t Standard deviation.

tt Coefficient of variation.

t Number of tests.

$$ Reported as LC50 - lethal concentration

However, data of this type are too limited at this time to be able to generalize these conclusions.

Water-soluble solutions of the insecticides aldrin (0.025 mg/1),

dieldrin (0.096 mg/1), and endrin (0.069 mg/1) were tested with the bioassessment protocol. Insecticide aggregates of all tests are summarized in Table 3.

Algae and Daphnia were quite sensitive to these substances, while Microtox and

the seed germination tests showed no effect. Earthworms were moderately

affected.

TABLE 2. EC50 TOXICITY VALUES FOR HERBICIDES*

Test Organism EC50** SDt CVtt Nt

Seed germination <0.17 0.017 10 20

Algae 54.35 19.02 35 8

Microtox, 30 min 68.20 9.82 14 8

Daphnia >126.55 41.76 33 8

Earthwormtt 11,315.00 2,772.00 25 8

* Modified from Miller et al. (1985).

•* Effective concentration at which 50 percent of organisms are affected.

Standard deviation.

ft Coefficient of variation.

t Number of tests.

N Reported as LC50 - lethal concentration

266
TABLE 3. EC5 0 TOXICITY VALUES FOR INSECTICIDES*

Test Organism EC50** SDt CVtt N

Algae 0.127 0.019 15 20

Daphnia 0.138 0.026 20 20

Earthwormtt 88.33 23.84 27 15

Microtox, 30 min NE§

Seed germination NE

* Modified from Miller et al. (1985).

** Effective concentration at which 50 percent of organisms are affected.

t Standard deviation.

ft Coefficient of vatiation.

t Number of tests.

t$ Reported as LC5 0 - lethal concentration

§ No effect.

Chemical Mixtures

In comparing the relative toxicity of 2,4-D acid (94 percent pure) with

the commercial Esteron 99 made up to the same 2,4-D concentrations, an interesting phenomenon was noted (Table 4). The response of algae, Microtox,

Daphnia, and earthworms to the Esteron 99 (with undisclosed "inert" ingredients) was much greater than it was for the 94-percent pure 2,4-D. This response suggests that the inert ingredients in Esteron 99 might be toxic themselves or that they act synergistically to enhance the actual toxicity of

2,4-D.

TABLE 4. EC5 0 TOXICITY VALUES FOR 2,4-D AND ESTERON 99*

2,4-D Esteron 99

Test Organism mg/I mg/1

Seed germination <0.1 <0.1

Algae 95.8 12.9

Microtox, 30 min 128.0 8.4

Daphnia >240.0 13.1

Earthworm** 9,830.0 12,800.0

* Modified from Miller et al. (1985).

** Reported as LC50 - lethal concentration

267
Hazardous Waste Site Samples

Greene and Peterson (1989) reported on the results of bioassay comparative toxicology assessments at 37 different sites spanning 23 states. They

conducted algae, Daphnia, and Microtox bioassays on 326 identically prepared

samples. More than half of the samples (185, or 57 percent) produced EC50/LC50

responses. Algae produced an EC50 for 158 (85 percent) of the toxic samples.

Daphnia produced an LC50 for 139 (75 percent) of the toxic samples. Collectively, algae and Daphnia produced EC50/LC5 0 for 177 (96 percent) of the toxic

samples. Each of the above experiences has contributed to a sense of confidence that the bioassay screening approach to hazardous waste site assessment

has merit.

Application to Remediation

Three chemical and one vitrification soil stabilization treatability

procedures were demonstrated at the Western Processing Site. Soils at the

site were contaminated with high concentrations of polynuclear aromatic hydrocarbons (PAH). The concentrations ranged from 8.0 to 740.0 mg/kg. Lead was

present at concentrations of 1,200 mg/kg, and zinc concentrations were in the

range of 5,000 mg/kg. A variety of engineering criteria were employed to

assess the success or failure of the stabilization procedures. Among them

were the Extraction Procedure (EP) Toxicity Test (Federal Register 1980), the

Toxicity Characteristic Leaching Test (TCLP) (Federal Register 1986), and the

Solid Waste Leaching Procedure (SWLP) (Green, unpublished data (USEPA), 1984).

The EP Toxicity Test was designed to extract and chemically screen for heavy

metals and selected pesticides. The TCLP was designed to ei:tract and chemically screen for heavy metals and organic contaminants. The SWLP was designed

to provide engineering estimates of the total amount of "leachates" that might

be expected from a site. The EP Toxicity and TCLP both employ chemical extractants, thus making them unsuitable for bioassay. The SWLP employs a

series of sequential leaches with distilled/deionized water to simulate hydrologic processes.

Unlike the initial chemical screening tests at this site, no PAH's were

detected when the soil stabilization demonstration was conducted. Therefore,

most analyses focused on heavy metals. Results of the EP Toxicity and the

TCLP are summarized in Table 5. According to engineering criteria, the chemical stabilization procedures all worked well. That is, they were all successful in reducing elutriate strengths to levels that allowed water quality criteria to be met directly. The vitrification procedure proved less successful.

When bioassays were applied to elutriates form each of the procedures,

various toxicities were shown (Tables 6 and 7). Vitrification (Battelle)

produced no toxicity, but was ineftective in terms of reducing leached

materials to levels acceptable by water quality criteria standards. Therefore, its lack of toxicity had little bearing on any decision concerning its

use as a stabilizer. However, since the other three procedures all worked

equally well, 'ut demonstrated various toxicity levels, the logical choice

might be to select the least toxic one (Chiyoda). It is interesting to note

that stabilization chemicals appear to have increased toxicity to the terrestrial test organisms. However, this "onsite" increase might be acceptable if

stabilization is successful in reducing contaminant migration offsite. :t

268
TABLE 5. LEACHING PROCEDURE COMPARISON*,**

Contaminant Total EP Toxicity TCLP

Zinc 5,000.0 68.000 68.000

Cadmium 27.0 0.360 0.020

Lead 1,200.0 0.530 5.100

Chromium 170.0 -- 0.045

Copper 110.0 0.047 0.170

Nickel 3.0 0.067 0.073

Barium 70.0 0.450 0.980

* Modified from Barich et al. (1987).

** Values expressed as mg/1 or mg/kg.

TABLE 6. AQUATIC BIOASSAY TOXICITY FOR TREATED SOIL

(Degree of Toxicity)*

Medium Algae Daphnia Microtox

Raw soil Extremely high Moderate None

Chiyoda High None Moderate

Calweld High Low Moderate

Soiltech Extremely high High Moderate

Battelle (vit.) None None None

* Modified from Barich et al. (1987).

must be considered in view of the total remediation picture. This demonstrates only one application of bioassays in the remediation process at hazardous waste sites. Several other applications can be made (Athey

et al. 1987).

The above series of evaluations and applications has led to a revised

Biological Assessment Protocol (Greene and Peterson 1990).

CONCLUSIONS

Application of bioassessment provides:

* Integration of all environmental and chemical variables.

* An indication of environmentally relevant toxicity potential.

269
TABLE 7. TERRESTRIAL BIOASSAY TESTS OF TREATED SOILS

(Degree ot Toxicity)*

Medium Root Elongation Seed Germination Earthworm

Raw soil None None None

Chiyoda Low Moderate Moderate

Calweld Low Moderate High

Soiltech Low Extremely high Extremely high

Battelle (vit.) Low None None

* Modified from Barich et al. (1987).

* A means of screening a wide variety of samples for acute toxicity.

0 An indication of media and organisms at greatest risk.

* A means of ranking problems based on ecotoxicology.

* A means of directing chemical analyses.

* Assistance in making engineering decisions regarding cleanup and

remediation.

ACKNOWLEDGMENTS

J. C. Greene, EPA Corvallis Environmental Research Laboratory, has been

instrumental in conducting evaluations of the biological assessment protocols

and in interpreting their responses to a broad spectrum of chemicals. J.

Barich, EPA Region 10, Seattle, has played a key role in designing and incorporating bioassays into the evaluation of remediation options. I thank them

for their assistance and support in preparing and reviewing this paper.

REFERENCES

Athey, L. A., J. M. Thomas, J. R. Skalski, and W. E. Miller. 1987. "Role of

Acute Toxicity Bioassays in the Remedial Action Process at Hazardous Waste

Sites," EPA-600/8-87/044, US Environmental Protection Agency, Environmental

Research Laboratory, Corvallis, OR.

Barich, J. J., J. C. Greene, and R. Bond. 1987. "Soil Stabilization Treatability Study at the Western Processing Superfund Site," Proceedings. 8th

National Conference--SUPERFUND '87, "November 16-18, 1987, Washington, DC.

Beckman Instruments, Inc. 1982. "Microtox System Operating Manual," Microbics Operations, Carlsbad, CA.

270
Danials, S. J. 1981. " Development of Realistic Tests for Effects and Exposure of Solid Wastes," Hazardous Solid Waste Testing: First Conference, ASTM

STP 760, R. A. Conway and B. C. Malloy, eds., American Society for Testing and

Materials, Philadelphia, PA, pp 345-365.

Federal Register. 1980. "Extraction Procedure Toxicity Test (EP Toxicity)",

Vol 40, Appendix 2 to Part 261, May 19, 1980, is amended July 7, 1981, Washington, DC.

Federal Register. 1986. "Toxicity Characteristic Leaching Procedure (TCLP),"

Vol 40, Appendix 1 to Part 268, November 7, 1986, Washington, DC.

Greene, J. C., and S. A. Peterson. 1989. "Comparative Toxicological Assessment of Hazardous Chemical Wastes Using Daphnia magna, Selenastrum

capricornutum, and Photobacterium phosphoreum," Society of Environmental Toxicology and Chemistry, 10th Annual Meeting: Transboundary Pollution, October 28-November 2, 1989, Toronto, Ontario, Canada.

Greene, J. C., and S. A. Peterson. 1990. "Protocols for biologically Assessing the Acute and Chronic Toxicity of Hazardous Waste Site Samples (Draft),"

US Environmental Protection Agency, Environmental Research Laboratory,

Corvallis, OR.

Keith, L. H., and W. A. Telliard. 1979. "Priority Pollutants: A Perspective

View," Environ. Sci. Technol. 13: 416-423.

Miller, W. E., J. C. Greene, and T. Shiroyama. 1978. "The Selenastrum capricornutum Printz Algal Assay Bottle Test: Experimenta' Design, Application,

and Data Interpretation Protocol," EPA-600/9-78/018, US Environmental Protection Agency, Environmental Research Laboratory, Corvallis, OR.

Miller, W. E., S. A. Peterson, J. C. Greene, and C. A. Callahan. 1985. "Comparative Toxicology of Laboratory Organisms for Assessing Hazardous Waste

Sites," Jour. Environ. Qual. 14(4):569-574.

Peterson, S. A., J. C. Greene, and W. E. Miller. 1989. "Biological Assessment of Toxicity Differences in Survival for Four Organisms Cultured in Sodium

Acetate Leaching Media and Elutriates of Municipal or Industrial Waste Leached

with Deionized Water or Sodium Acetate Leaching Media," Symposium on Waste

Testing and Quality Assurance (in press), Vol 2, ASTM STP 1062, David Friedman, ed., American Socitty for Testing and Materials, Philadelphia, PA.

Porcella, D. B. 1983. "Protocol for Bioassessment of Hazardous Waste Sites,"

EPA-600/3-83/054, US Environmental Protection Agency, Environmental Research

Laboratory, Corvallis, OR.

Roop, R. D., and C. T. I'unsaket. 1985. "Biomonitoring for Toxics Control in

NPDES Permitting," Jour. Water Pollut. Control Fed. 57:271-277.

271 '- -" . ..
FOLLOW-UP INVESTIGATION OF MARINE LIFE AROUND ARTIFICIAL SANDY BEACH OF

YOKOHAMA MARINE PARK AND PROBLEMS CONCERNING MAINTENANCE

T. Tanaka

CDD, PHB, YCG

4th Floor, Industrial and Trade Center Building

Yamashita 2, Naka-ku, Yokohama, Japan

D-P006 469

Most of the natural shoreline in Yokohama City

has been lost due to coastal land reclamation executed

since the opening of the port.

INTRODUCTION

Yokohama City executed the land reclamation work off its Kanazawa section during the period 1971 to 1988 to accommodate factories and other establishments which had to evacuate from the city center in compliance with the

City Center Redevelopment Plan.

In this connection, construction of a marine park and development of the

artificial island called "Hakkei-jima" have been promoted to restore the

shoreline which has been lost because of the land reclamation and to provide

recreational facilities for citizens.

This paper reports the results of the follow-up investigations conducted

through the past 10 years about marine life which has settled at the "artificial sandy beach," a main feature among the facilities in the marine park, and

also describes problems concerning the maintenance and management of the

beach.

ARTIFICIAL SANDY BEACH PROJECT

The basic concept for the construction of a marine park initiated in

February 1971 was to "create a broad sandy beach where f:hi and shellfish live

and people can gather shellfishes" (Yokohama City Government 1981).

This area is well known traditionally as "Kanazawa Hakkei," a scenic

spot; the beach portion of the marine park project appeared in Hiroshige's

Ukiyoe "Otsutomo-no Kihan" (Photo 1). Until t-he 1960's, the beach was a

famous spot for shellfish-hunting. Therefore, in the planning, a primary target was to create a shoreline matching present-day requirements, while considering the historical background, and to make the beach a place where marine

c-eatures live and people can gather shellfishes and participate in marine

recreational activities such as promenading and bathing. Then, there emerged

a sandy beach approximately 1 km long and 200 m wide at ebb tide or b0 m wide

at high tide. Approximately 1.1 million cu m of pit sand with a median gr-in

di-imeter of 50 - 0.25 mm was brought from Mt. Sengen, Chiba I'Lefecture,

272 92-10789

92 4 22 2I2,I! 1111 1 li Il l4l 

L .... ...._ _.. .._ _ ...... .
Photo 1. Yokohama--Marine Park sandy beach and

Hakkei-jima Island

across Tokyo Bay, then temporarily deposited at the sea bottom for 5 years,

and finally pumped with a pump dredge to make a beach (Kobayashi, Sugiyama,

and Tanaka 1980).

INHABITATION EXPERIMENT WITH SHORT-NECKED CLAMS

IN NOURISHED BEACH SAND

Since the sand used for beach nourishment is from inland, a test station

was constructed with this sand on the existing beach covered by the project

from October 1976 tG January 1977 to learn if short-necked clams (Ruditapes

philippinarum) could live in the beach after nourishment (Coastal Development

Dept. et al. 1977). A number of short-necked clams from the neighboring beach

were collected, marked, and planted around a polyvinyl chloride pipe signpost

erected at the center of each of the test zones. Then, how the clams inhabitated, grew, and moved was investigated. Also, the secular change in the

variety and individuals of benthos, water quality (temperature, specific

gravity, pH, DO, COD, SS, CI, and colon bacilli), and bottom material (ignition loss, COD, sulphides, and oxidation-reduction potential) was observed.

As the result, it was found that short-necked clams could live well and

grow even in the pit sand, which varied only slightly from the existing tideland. Also, from this it is apparent that the variety of benthic creatures

273
has become more diverse as time goes by, and the sand used for beach nourishment is no particular hindrance to the environment in which benthic creatures

other than short-necked clams could live.

PLANNING OF ARTIFICIAL BEACH AND INVESTIGATION OF BENTHOS

In March 1979 the "Construction Technical Manual of Artificial Beach"

was compiled by the Ministry of Transport. In this work, "the creatures'

inhabitable environment at an artificial sandy beach and prediction of change

in the bottom material which makes up its life base" was considered as lacking

in knowledge sufficient for the working group to describe. Moreover, around

1971 when this sandy beach plan was introduced, little was known even about

the phenomenon of littoral drift which would greatly affect the stabilization

of the sand deposited, in spite of the task to reproduce a shellfish-gathering

place (Coastal Development Dept. et al. 1979-1988). Therefore, an implementation plan was set up from all pieces of information available at this planning

stage, and construction of a sandy beach started. At the same time, it was

decided to fill any gaps which would appear later by follow-up investigations

and to employ adequate control measures as the construction work progressed.

Accordingly, various investigations were conducted right after the construction of the sandy beach and followed changes in the environment and life

at the sandy beach. Items, purposes, and times of investigations are shown in

Table 1. Survey points, survey courses of traverse, neighboring topographical

features, and sandy beach profiles are shown in Figures I and 2, respectively.

The existing seminatural beach of Nojima was added in the fiscal 1983 to

the scope of investigation for comparison with the artificial beach.

FORM OF SANDY BEACH AS LIFE BASE FOR CREATURES AND ITS CHANGE

After the wave observation by the wave meter at the Kanazawa Bay entrance, the comparison of topographical features before and after reclamation,

and the examination of short-necked clams' living environment based upon the

research concerning the life history of existing short-necked clams, the following preconditions were set up to determine sectional and plane forms of the

beach:

a. The sea should be calm and the wave height should be no higher than

about 80 cm (Ho' - 0.8 m, T - 5 sec).

b. The depth of water should be no greater than -5 m.

c. The existing bottom slope sbould be gentle as about 1/100 on the

average.

d. Living space for creatures should be maintained in the shallow part,

mainly during the period between tides.

e. Sand movement should occur so as to allow habitation of creatures and

to prevent aging of the beach.

274
2. 4

r-- -~ -------.

- .............

K- - -- Il i I.. ....... 1

Lr

P-4_ _ _ _ 7
,e..

07

9P Hakkeijima

01 (Artificial Island)

10,

Kanazawa Pump Station ,

ISO^C 27

Jt to2 28

4' Nojitma

Beach 12' Nissan Automotive Plant

Nojima

0 100 200m

Figure 1. Survey points and courses of traverse

276
E

0

0

44

.

0

-.4

4

0

10

.4-

4'4

E 0

I 0 L

LNU

CLU

277O
f. Aeration and a seawater exchange function to purify seawater should

be provided. That is, the breaker zone should be wide and gentlesloped, and no structure to create a stagnant water area should be

built.

Taking all of the preconditions into consideration, the beach profile

was designed with foreshore slope of 1:30; inshore slope of 1:100, the same as

the existing bottom slope; and beach width of 90 m.

A plane form was determined from the results of an on-the-spot survey of

the form of a wave crest line and the pocket beach.

As shown in Figure 2, the sectional form of the beach measured about

4 years after the formation is 1:100 in a depth greater than +1.0 m, which is

almost the same as the design slope, and 1:5 to 1:10 from the intermediate

tide zone shallower than +0.5 m to the high tide zone crest, though fluctuating seasonally. Thus, the beach is stabilized (Tanaka 1980).

WATER QUALITY AT BEACH

Water Temperature

Temperature of the water was high in summer and low in winter, regularly

changing in a range from 7° to 260 C.

Hydrogen Ion Concentration

The maximum concentration was 8.9 in 1980 and 1983, and the minimum over

7.8 very year.

Chlorine

The average was about 17 percent with no particular change except during

fiscal year 1983, in which it dropped below 10 percent.

Dissolved Oxygen

Maximum value was 18.9 mg/i in fiscal year 1985 and 13 mg/1 in every

other year. Minimum value was 2.5 mg/1 in fiscal year 1981 and over 4 mg/i in

every other year. Average value was generally 7 to 9 mg/i. No particular

change was observed.

Chemical Oxygen Demand

Maximum value was 15.9 mg/1 in fiscal year 1985, and the minimum value

was 1 to 2 mg/i in every fiscal year. Average value was 3 to 5 mg/i. No

particular change was observed.

Total Nitrogen

Maximum value was over 2 mg/i in fiscal years of 1982, 1983, and 1985,

but the average value was 1.4 to 1.4 mg/i. No particular change was observed.

278
Total Phosphorus

The maximum value exceeded 2 mg/2 in the fiscal years from 1981 to 1985,

but the average value showed a declining trend to below 0.1 mg/A from fiscal

year 1986.

The water quality at the artificial beach (Figure 3) was better than

that at the neighboring Nojima beach or Nojima channel (Coastal Development

Dept. et al. 1979-1988). It deteriorates a little in summer and recovers in

winter. When viewed over time, it has made almost no change since the beach

construction.

BOTTOM MATERIAL OF SANDY BEACH

Figure 4 shows the secular change of the ignition loss of the bottom

material and the grading composition (in September 1988) by the water area

from the tideland area at the beach to the offing.

The ignition loss of the bottom material in the tideland area has been

more or less 1.0 percent, which is almost no change to date from the time of

beach construction. In the shallow water area with a depth of about 1 m, the

ignition loss of the bottom material has been 1.0 to 2.0 percent, which shows

no substantial difference from that in the tideland. The ignition loss in the

water area with a depth about 3 m was somewhat high in fiscal year 1982, but

it showed a decrease thereafter and became less than 3 percent in and after

fiscal year 1984. Of the existing bottom material with a depth of 5 to 7 m,

it was about 6 to 7 percent until fiscal year 1986, but showed a declining

tendency thereafter. As to the grading composition, sand (grain diameter

0.074 to 2 mm) was predominant at the survey point where the ignition loss was

low, but silty clay (grain diameter less than 0.074 mm) was predominant in the

offing where the ignition loss was high. The median grain diameter tended to

become larger in the tideland area and smaller in the offing.

Thus, the bottom material of the Kanazawa Bay is corresponding well with

the depth of the sea (Coastal Development Dept. et al. 1979-1988). Therefore

it is considered that the tideland and shallow-water areas at the beach are

not only suitable for shellfish-gathering to be patronized by citizens but are

also important as water areas for purifying the seawater by aeration of breaking waves and promoting decomposition of organic matters, and for providing a

habitat for marine creatures.

BENTHIC CREATURES AT BEACH (HABITATION OF MAINLY LARGE BENTHIC

CREATURES SUCH AS SHORT-NECKED CLAMS)

Appearance of Benthic Creatures

Immediately After Artificial Beach Construction

The artificial beach construction work was executed from June 25 to

September 2, 1979, by the pump dredge. In December 1979, three months after

the completion of the sandy beach, shellfishes Mactra venerifcrmis and Mactra

chinensis appeared in large quantity, and in a half year these shellfishes

increased as much as 900 g/m2 , larger toward the peninsula. This phenomenon

is considered as influenced by tidal currents (Figures 5 and 6). In

September,

279
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= - - m

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(%) Legend

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10.0 - 0-. - o Site 300 m from Control Point (Depth: about 1 m)

- "Site 450 m from Control Point (Depth: about 3 m)

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8.0 k

6.0 - S - J -- ~

4.0 -

2.0 -o. .

0 I I I I I I

1980 1981 1982 1983 1984 1985"* 1986 1987 1988

Figure 4. Secular change of ignition loss of bottom material

(investigated in September every year)

I year after the completion of the beach, many spats of short-necked clams had

appeared.

Secular Change of Benthos

Figure 7 shows the secular change of the average value of the large

benthic creatures which were collected in a 1-m-square section at each of the

12 survey points in the tideland area (average ground height +0.4 m) at the

artificial beach and screened by a 5-mm sieve.

In about 1 year after the completion of the beach, short-necked clams

became the dominant species, and other shellfishes such as Mactra veneriformis

and Mactra chinensis increased gradually. For the last 3 years, short-necked

clams have been maintaining a population density at 800 to 1,000 g/m2. Mactra

chinensis inhabited most densely at about 500 g/m2 in March 1980, shortly

after the completion of the beach, but decreased to 100 g/m2 in fiscal year

1983. Mactra veneriformis were many initially, and in fiscal years 1982 and

1983. At peak, its population density reached 400 g/m2 but reduced to less

than 100 g/m2 after fiscal year 1986.

In comparison with the Nojima beach, which is the only natural beach

left in Yokohama, the artificial beach showed an increase in the number of

short-necked clams.

Thus reproduction of the shellfish gathering-place as one of the objectives of the artificial beach in the marine park is considered successful. A

pattern that the shellfish population decreases in the springtime and recovers

in the wintertime has set cyclically, as there were so many people (50,000 at

most on one day) who visited the beach in the springtime to gather shellfish.

However, the biggest trouble is the reckless hunting of spats less than

20 mm in shell length by shellfish merchants. Thus, such natural resources

may be exhausted, and so an appeal is being made to the people by signboard

and handbill.

281
September 1979:0 WtWegt

L........................... We Ind ividu l

500 50

0 40 

300 30

" 20 20

0 1

(Izdividuals/m) 1 3 5 7 Survey Point ("/m*)

- Kanazawa Pump Station Peninsula -,

December 1979

400 2000

300 1500 1-

200 1000

too S oo

C 0

1 3 5 7 Survey Point

(Individuajs/m2) - Kanazawa Pump Station Peninsula - ('/m,)

..............................

March 1980

S00 6.000

500 1500

. 400 14000

-I

5~ 0 ooo

300 3000

(Individuals/m ) 0 (/i)

3 7 Survey Point

i anazawa Puic)D StaLon Penins$ul. --

Figure 5. Generating condition of creatures immediately after

construction of artificial beach

282
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284
EMERGENCE OF CREATURES OBSTRUCTIVE TO GROWTH OF SHORT-NECKED CLAMS

What causes the obstruction of the growth of short-necked clams, a main

item to be hunted by people at the beach, is described here. According to the

research made so far, there are two types of creatures harmful to the existence of short-necked clams, one feeding on them directly and the other checking the growth of them indirectly.

Those creatures who directly feed on short-necked clams are fishes known

as black porgies (iyllo macrocephalus), surf fishes (Ditrema temmincki), eels,

gobies (Gobiidae), and flatfishes; sea snails such as Reishia clavigera,

Reishia bronni, Rapana venosa, and Glossaulux didyma; and octopuses such as

Octopus vulgaris, Octopus ocellatus, and Octopus minor. Also, such Crustacea

as Charybdis japonica, Leucosia obtusifrons, Gaetice depressus, Paleomon

Ortamanni, and Upogebia major eat spats of short-necked clams.

Among birds, the Aythya are known traditionally to feed on spats in the

farms of short-necked clams and clams built on the inner parts of the Tokyo

Bay. Besides, starfishes are known to do considerable damage on them.

No particular problem has arisen so far around the artificial beach in

connection with such enemies. However, Musculus senhousta, a bivalve species,

and Ulva lactuca, a seaweed, which exert the most adverse influence indirectly

on them, have appeared. From around September 1980, Musculus senhousis were

seen to have settled extensively on the sea bottom around the beach and from

the following spring. Ulva lactuca were seen to have grown in a large

quantity. Their areas of distribution were almost the same. As shown in Figure 8, they were more abundant in areas near the peninsula with the artificial

beach in the marine park and near the Nissan Automotive Plant on the Nojima

coast. It seems that tidal currents are tied up in these areas.

Formerly used as feed for cattle for fertilizer, or as a substitute for

the green laver (Moritoshi and Shinzaki 1980), Ulva lactuca not only adversely

affects the habitation of short-necked clams but also contaminates the beach

after bein, thrown there by waves and decomposing.

To investigate the status of Ulva lactuca, an inquiry was sent to prefectural fisheries experiment stations around the Mikawa Bay and the Inland

Sea where Ulva lactuca was believed to be increasing. It was essential to

know the damage it had inflicted on fisheries and tLe method of removal, in

and after 1982, besides gathering data available at that time.

As a result, the growth environment of Ulva lactuca can be generally

summarized (World Ocean System, Inc. 1980) as follows:

a. A water area ranging from the middle part of intertide zone to the

upper part of gradually deepening zone (depth: 0.5 to 5.0 mm).

b. A water area where tidal currents run slowly, i.e., the inner part of

bay.

c. Locating in the vicinity of the river mouth.

d. Settling at places with bedrock, reef, tetrapod, or revetment.

285
NojmaKanazawa Main Park~ N~.;m Pump Station

NojimaCnl ~4

Nisan Automotive PlantPniua

( Hakk~ejima

(Antificial Island) f 3 10 70,

Jaualy 199

Nojimae Kanazaw Cr

Figure 8.Dipstibtiion o la.at

Nojima C286
q. Floating on tidelands where the bottom is sandy or muddy, or in a

shallow water.

. Accumulating on a corner of a sea area as blown away by winds.

Z. Daylight and sea water temperature showing little bearing upcq the

growth of it, apart from its qtvantity being more or less, as it grows

from Hokkaido in the north to Okinawa in the south.

The reason for the abnormal propagation of Ulva lactuca is not known

yet. As far as the artificial beach here is concerned, the direct cause which

seems very probable is that Mactra veneriformis has formed a foundation for it

to settle down.

From the answers to our inquiry, it is known that nobody is considering

at the present time how to remove Musculus senhousia or Ulva lactuca. Therefore, from July to September 1982, with a small pump dredge of 270P Class S,

Ulva lactuca and Musculus senhousia were pumped up together with sand in a sea

area of 1.75 ha with a depth of 0 to 3 m around the artificial beach and then

sent through a mud pipe into the reclamation site earmarked for the construction of an offshore artificial island "Hakkeijima." The volume of the sand

obtained by dredging was roughly 25,000 cu m. The average thickness dredged

was 14.2 cm. Afterward, Ulva lactuca was removed by ketaami from the springtime to the early summertime, in which period it was expected to grow up

(Table 2).

In July 1988, the artificial sandy beach was opened to the general public as a municipal sea-bathing place. However, in or about 1986, appearance

of oysters (Crassostrea gigas) as a new creature was recognized (Figure 9).

Therefore, from April to June 1988, prior to the opening of the beach, oysters

amounting to roughly 19 tons were moved by dragnet and by hand-picking because

of their danger to bathers.

From the fact that various marine creatures incliding such useful fishes

and shellfishes as short-necked clams and Mactra chinensis live in this area,

it is assumed that the marine environment around the artificial beach is improving considerably (Port of Yokohama Promotion Association 1988).

CONCLUSION

As mentioned above, the authors conducted various investigations for the

past 10 years to obtain information to use partly for the maintenance and

management of the artificial sandy beach in the Marine Park of Yokohama City.

This paper summarizes the result of such investigations as relating to the use

of the beach for shellfish-gathering and sea bathing.

Many things are still unknown to us about how creatures generate and

about the environment in which they inhabit, and we are reminded anew of how

complicated the mechanism of nature is and how difficult it is to foresee such

a mechanism. Traditionally, sea bathing and shellfish-gathering should be

recreational activities on the natural beach, and the generation of such

things as green laver (Ulva lactuca) and oysters is considered as a natural

phenomenon, not as an occurrence harmful or unpleasant to humans.

287
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00 4

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00 E -CI

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00

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288
Legend

W:Over 1,000 glm2

100-i .OOg~m,

Jurmu 198

Figure 9. Distribution of oysters (Crassotrea gigas)

289
However, for the beach to be useful as a comfortable place for people,

removing these things by artificial means is inevitable, though it is against

the law of nature. Thus, the development of an effective removal method is

expected in the future for the maintenance and management of this artificial

sandy beach.

Together with these measures, artificial problems--for example, generation of waste, disposal of refuse, and protection of spats against reckless

hunting-- can be solved by improved manners of the people using the beach for

the maintenance of a good environment there.

For the utilization of the sea area around the beach, a steady investigation of this is to be carried out continuously, with an interdisciplinary

effort (engineering and biology), while the people engaged in the project must

regard nature with humbleness and reverence.

REFERENCES

Coastal Development Dept., Urban Development Bureau, Yokohama City, and ShinNihon Meteorological and Oceanographical Consultant Co., Ltd. 1977 (Mar).

"Report of Short-necked Clam Transplantation Tests and Benthos Investigations

in Mt. Sengen Pit Sand on Reclaimed Land off Kanazawa."

Coastal Development Dept., Port and Harbor Bureau, Yokohama City and ShinNihon Meteorological and Oceanographical Consultant Co., Ltd. 1979-1988.

"Investigation Report of Benthic Fish and Shellfishes at Artificial Beach in

Connection with Construction of Marine Park on Reclaimed Land off Kanazawa."

Kobayashi, ?, Sugiyama, ?, and Tanaka, T. 1980 (Sep). "Planning and Execution of Sandy Beach Construction in Marine Park, Yokohama City," Journal of

Japan Society of Civil Engineers, pp 53-60.

Moritoshi, ?, and Shinzaki, T. 1980 (Sep). "Tales of Seaweeds," Publishing

Society, Tokai University, pp 63 and 195.

Port of Yokohama Promotion Association. 1988 (Aug). "Fish Watching,

Yokohama--Fish and Shellfishes in Marine Park," edited by Yokohama City Port

and Harbor Bureau.

Tanaka, T. 1980 (Dec). "Planning and Execution of Artificial Beach and Back

Park Land Construction," Japan Construction Engineers Association, pp 47-58.

World Ocean System, Inc. 1980. "A Feasibility Study of Ulva lactuca as

Energy Source."

Yokohama City Government. 1981 (Feb). "Basic Concept of Marine Park,

Yokohama City."

290