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Assessment and Remediation of Contaminated Sediments (ARCS) Program

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Prepared by
U.S. Army Engineer District, Detroit
Detroit, Michigan

For the
Assessment and Remediation of Contaminated Sediments
(ARCS) Program
U.S. Environmental Protection Agency
Great Lakes National Program Office
Chicago, Illinois

Pilot-Scale Demonstration of Sediment Washing for the Treatment of Saginaw River Sediments

US Environmental Protection Agency. July 1994. Abstract and Table of Contents to "Pilot-Scale Demonstration of Sediment Washing for the Treatment of Saginaw River Sediments," EPA 905-R94-019. Chicago, Ill.: Great Lakes National Program Office.


This report presents the results of a pilot-scale demonstration of the remediation of PCB contaminated sediments from the Saginaw River. A sediment washing system developed by Bergmann USA was evaluated for its effectiveness in remediating sediments by separating PCB and metal enriched physical phases from the bulk of the sediment. Sediments were processed using various classification devices and water flow configurations. Samples were collected at up to 23 points throughout the system to monitor grain size distributions, densities, and total organic carbon content. Samples from selected stations were analyzed for PCB and metal concentrations.

Approximately 80% of the solids contained in the feed were recovered as a washed sand product. The remaining particulates were recovered as oversize material (5 to 15%), particulate organics (<2%), and fine particulates (8 to 9%). The process resulted in a 82% reduction in PCB concentration when comparing the feed (1.2 mg/kg) to the washed sand (0.21 mg/kg). Reduction percentages for other constituents were calculated as follows: sub-38u particles (94%), sub-75u particles (77%), total organic carbon (79%), cadmium (88%), chromium (55%), copper (65%), mercury (82%), nickel (71%), lead (61%), and zinc (82%). These constituents tended to be concentrated in the fine material fraction, and to a slightly lesser extent in the particulate organics.

Sediment washing is a relatively low cost treatment option when compared to other technologies commonly considered for the remediation of contaminated sediments. Treatment and monitoring of 10,000 cubic yards (cy) using a 50 tons per hour (tph) plant is estimated to cost about $54/cy. Treatment of 100,000 cy using the same plant would be expected to cost about $23/cy. Operation of a full-scale unit capable of treating 50 tph would be expected to result in the recovery of slightly less material as washed sand, but in a higher percentage reduction of contaminants.

Table Of Content 

List of Figures
List of Tables
List of Abbreviations and Symbols Introduction
Description of the Saginaw River/Bay Area of Concern
Watershed Description
Status of Remedial Action Plan
Sediment Physical/Chemical Character
Sources of Sediments
Sediment Pollution
Sediment Characteristics and Quality

Demonstration Approach
Technology Selection
Planning Document
Environmental Assessment
Scope of Work/Contract
Sample Location and Excavation
Site Description
Site Preparation
Plant Assembly
Material Handling
Transport and Storage
Feed Operations
Sediment Washing
System Description
Removal of Oversized Material
Hydrocyclone Separators
Dense Media Separator
Attrition Scrubber
Additional Washing Steps
Sand Recovery and Dewatering Screens
Pilot-Scale Demonstration
Fall 1991 Operations
Spring 1992 Operations
Residuals Management
Execution and Costs
Operations Monitoring by Bergmann USA
Material Process Monitoring under the
Corps of Engineers Material Process Monitoring
Parameter Selection
Analytical Protocol

Results and Discussion
Laboratory Results
Overall Mass Balance
Physical Characteristics & TOC
Overall Performance
Rotary Trommel
Hydrocyclone Separator Number 1
Dense Media Separator
Attrition Scrubber
Hydrocyclone Separator Number 2
Hydrocyclone Separator Number 3
Sand Recovery Screen
Rotary Screen
Split Deck Dewatering Screen
Polychlorinated Biphenyls (PCBs)
Process Feed
Washed Sand
Particulate Organics
Clarifier Feed
Recycle Water
Saginaw Bay Water
SITE Results
Sediment Toxicity
Full-scale Implementation
Full-Scale Treatment System
Material Feed
Sediment Washing Unit
Cost Estimate for Sediment Remediation
Remediation of 10,000 Cubic Yards
Remediation of 100,000 Cubic Yards
Conclusions and Recommendations
Material Composition
Material Handling
Processing Operations
Contaminant Removal Levels
Analytical Surrogates
Recommendations/Lessons Learned

References 85
Appendices 87

Appendix A Compiled Data from Laboratory Analyses
Appendix B Data Reports from Laboratory Analyses
Appendix C Schematic Diagrams Illustrating Daily Modes of Operation
Appendix D Quality Assurance Project Plan


The 1987 amendments to the Clean Water Act, Section 118(c)(3), authorized the United States Environmental Protection Agency (USEPA) Great Lakes National Program Office (GLNPO) to conduct a 5-year study and demonstration project on the control and removal of toxic pollutants in the Great Lakes, with emphasis on the removal of toxic pollutants from bottom sediments (U.S. Environmental Protection Agency, 1990). The Great Lakes Water Quality Board of the International Joint Commission (IJC) has documented 43 Areas of Concern (AOC) in the Great Lakes Basin where one or more of the objectives of the 1978 Great Lakes Water Quality Agreement and other jurisdictional standards, criteria, or guidelines are not met. GLNPO initiated the Assessment and Remediation of Contaminated Sediments (ARCS) Program to assess the nature and extent of bottom sediment contamination at selected AOCs, evaluate and demonstrate remedial options, and provide guidance on the assessment of contaminated sediment problems and the selection and implementation of remedial actions in the AOCs and other locations in the Great Lakes.

Past industrial and municipal discharges have polluted the Saginaw River and Bay and their sediments. As a result, the river exhibits environmental degradation and impairment of beneficial uses of water and biota (Michigan Department of Natural Resources, 1988). Under the 1987 amendments to the Clean Water Act, Section 118(c)(3), the Saginaw River and Bay AOC was one of five areas designated for priority consideration in locating and conducting demonstrations of sediment assessment and remediation techniques (Figure 1). A pilot-scale demonstration was conducted in Saginaw Bay, Michigan in the Fall of 1991 and Spring of 1992 to evaluate the ability of a sediment washing process to remediate Saginaw River sediments contaminated with polychlorinated biphenyls (PCBs).


The objective of the Saginaw River pilot-scale demonstration was to evaluate sediment washing as a treatment technology for sediments from the Saginaw River and Bay Area of Concern. Specific objectives of the pilot-scale demonstration included determining: the efficiency of the sediment washing process in separating silts, clays and particulate organics from predominantly sandy sediments; the effectiveness of various components of the system in achieving the desired separation; the handling and pre-processing requirements for the sediments; and the characteristics of each of the process output streams and their suitability for reuse or disposal. Another objective of the demonstration was to provide information to be used in the development of cost estimates for full-scale remediation projects.


Watershed Description
The Saginaw River and Bay Area of Concern is defined as extending from the outer edge of the Bay, between Au Sable Point and Point Aux Barques, upstream to the head of the Saginaw River. The Bay is 52 miles long, up to 26 miles wide, and has a surface area of 1,143 square miles. The River extends inland for 22 miles to its head at the confluence of the Shiawassee and Tittabawassee Rivers above the City of Saginaw (Figure 2). These rivers, along with the Flint River (a tributary of the Shiawassee), and Cass River (a tributary of the Saginaw), drain a large part of the central portion of Michigan's lower peninsula, and contribute about 75% of the hydraulic flow to the Bay. The Saginaw River watershed along with the 27 other smaller rivers, creeks and agricultural drains which enter Saginaw Bay directly, drain about 15% of the State's land area (about 6,278 square miles). Much of this watershed is outside the Area of Concern, but the entire drainage basin is considered part of the Source Area of Concern (Figure 3) as anthropogenic inputs from throughout the area may contribute to the problem of impaired usage.

The majority of anthropogenic contaminants derive from agricultural run-off, and municipal and industrial discharges in the cities of Flint, Saginaw, Bay City and Midland. These inputs have resulted in degradation of the resource value of the Saginaw River. The Michigan Department of Natural Resources 1988 Remedial Action Plan (RAP) for the area describes 6 beneficial uses that are impaired. These include: public drinking water supply, human consumption of fish, total body contact recreation, commercial navigation, shoreline aesthetics, and the suitability of the area to support indigenous aquatic life. The impairments are due to excess nutrients, toxic materials including PCBs, dioxin and heavy metals, and bacterial contamination. Sources continuing to contribute these contaminants include industrial and municipal discharges, combined sewer overflows (CSOs), contaminated sediments, urban and agricultural run-off, waste disposal sites, and atmospheric deposition. While the sediments in the AOC are contaminated, they are not considered 'toxic' or 'hazardous' based on the regulatory definitions of the Toxic Substances Control Act (TSCA) or the Resource Conservation and Recovery Act (RCRA).

Status of Remedial Action Plan
The Michigan Department of Natural Resources (MDNR) is responsible for the development and implementation of a Remedial Action Plan (RAP) for the Saginaw River/Bay AOC. The East Central Michigan Planning and Development Region (ECMPDR), a regional planning agency in Saginaw, prepared an initial draft RAP under contract with MDNR. A variety of representatives of local, state and Federal agencies, academia, environmental consulting firms, and public interest environmental groups also participated in development of the RAP. The Saginaw Basin Natural Resources Steering Committee, a group of representatives from the general public, interest groups, and industry in the drainage basin, coordinated public participation through meetings and workshops. The first draft RAP was completed in 1987. A revised version was distributed for public review, and subsequently submitted to the International Joint Commission (IJC) in September 1988.

The RAP identified as goals: (1) reducing the levels of toxic materials in fish tissue to the point where public health fish consumption advisories are unnecessary, (2) reducing toxic material levels in the AOC to meet Michigan water quality standards and (3) reducing eutrophication in Saginaw Bay to a level where the Bay will support a balanced mesotrophic biological community. Actions taken since the 1988 document can be classified in six general areas: Coordination, Nonpoint Source Pollution Reduction Projects, Point Source Facility Improvements/Controls, Environmental Assessment/Research Projects, Education Programs, and Miscellaneous Activities. Among these areas there have been approximately 90 separate efforts to make progress towards improving the AOC. Additional information concerning these programs or projects can be obtained from the December 1992 Saginaw River/Bay Remedial Action Plan Progress Report.

Sediment Physical/Chemical Character

Sources of Sediments--
Agricultural activities account for over half the land use in the Source Area of Concern. As a large portion of this land is rich in erodible clay, runoff from these areas is the likely source for the majority of sediment entering the system. Sedimentation occurs in the navigation channels of the River and throughout much of the Bay. The 1988 RAP reported apparent sedimentation rates of up to 0.67 g/cm2/yr in the Bay. Corps of Engineers (COE) dredging required to maintain the Federal Navigation Channels of the Saginaw River removes about 35,000 cy of sediments annually. Maintenance of the Saginaw Bay channel requires the dredging of approximately 300,000 cy on an average annual basis.

Sediment Pollution--
The 1988 RAP identifies a wide variety of contaminants which have been found in the tributaries of the Saginaw River. Located within these tributary watersheds are a variety of large and small chemical and manufacturing companies. Contaminants found in these watercourses include polynuclear aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), dichloro-diphenyl-trichloro-ethane (DDT), polybrominated biphenyls (PBB), poly-chloro dioxins, and a variety of metals. Saginaw River sediments have also been contaminated by other industrial and municipal discharges. PCBs were found in the suspended solids recovered from the river as early as 1971. Since then concentrations in the sediments outside the navigation channel have been found exceeding 500 mg/kg in a few spots (MDNR, 1988). Navigation channel sediments are more typically in the <.1 to 5 mg/kg range. The navigation channel material can be described as moderately contaminated with PCBs. Over a decade long record, the material has not indicated any hazardous (RCRA) nor shown any toxic (TSCA) characteristics. Other categories of sediment parameters that are elevated consist of nutrients and general organics. The latter (TVS, TOC, COD, etc.) are primarily derived from degraded detrital matter. An unquantified minor portion of general organics is likely contributed by petroleum products. Heavy metals are in background ranges commonly found in Great Lakes sediments.

Sediment Characteristics and Quality--
A COE Detroit District field crew sampled the maintained navigation reach in July 1992 utilizing gravity coring. The results show that the sand size fraction of the sediments increases in the upriver direction. Within a mile of the mouth, the sediment was about 15 to 20% sand size, increasing to a range of 70 to 99% at the upriver reaches near Carrolton. Detrital material was abundantly present, contributing to elevated organic indicating parameters including Total Organic Carbon (TOC), Solvent Extractables (O&G), Total Volatile Solids (TVS), and Chemical Oxygen Demand (COD). This set of analyses, as in previous years, showed heavy metals at insignificant concentrations (i.e. at background levels frequently encountered in Great Lakes sediments). Arsenic, ranging from 5 to 20 mg/kg and averaging around 9 mg/kg, is a good example.

PCBs, while still present and quantifiable showed a marked decrease, ranging from a high of 25 mg/kg and an average of approximately 1 to 2 mg/kg in the previous decade, to a high of 1.5 mg/kg and an approximate average of 0.1 to 0.2 mg/kg as seen in analyses carried out in 1992 and 1993. The overall channel sediment quality, while appearing to be demonstrating an expected trend of decreasing PCB levels, remains contaminated with quantifiable levels of PCBs which are readily available for biomagnification processes in the aquatic environment. Accordingly, these sediments may be described as contaminated with PCBs, and removal from the aquatic environment remains a highly desirable objective.

The sediment dredged for use as feed material was relatively sandy as shown in Table A-20. The heavy metal and PCB concentrations of this material are presented in Table A-26. The values shown are typical of the range of values observed over a two decade period in the Saginaw River Federal navigation channel. However, as we have just noted, the mean PCB value of 1.2 mg/kg found in the feed would presently be considered a high value for the overall channel based on the analyses carried out in 1992 and 1993.


  1. Five Areas of Concern designated for on-site ARCS Pilot-Scale Demonstrations
  2. Major tributaries to Saginaw Bay
  3. Location of the Saginaw River/Bay Area of Concern
  4. Location of dredging and processing areas
  5. Layout of Pilot-Scale Demonstration site for sediment washing at Saginaw Bay, MI
  6. Feed hopper and conveyors, and sand discharge conveyor
  7. General process flow diagram for the Bergmann USA system used at Saginaw Bay
  8. Barge-mounted Bergmann USA sediment washing plant at Saginaw Confined Disposal Area
  9. Rotary Trommel showing headbox, upper washing zone, and lower sizing zone
  10. Hydrocyclone Separator Number 1, mounted above the Dense Media Separator
  11. Schematic of a Linatex Hydrocyclone Separator
  12. Schematic of Linatex Dense Media Separator
  13. Hydrocyclone Separators Numbers 2 and 3, showing feed lines with pressure valves, overflow lines with smaller vacuum control lines, and underflow discharge to box below
  14. Clarifier used during Spring 1992 operations
  15. Sampling points for ARCS Pilot-Scale Demonstration at Saginaw Bay
  16. Procedure No. 1, particle sizing less than 38 microns
  17. Procedure No. 2, particle sizing greater than 38 microns
  18. Grain size distribution of feed
  19. Grain size distribution of four discharge streams
  20. Enrichment Factors for TOC in feed, fines, particulate organics and washed sand
  21. PCB concentrations of 4 hour composite samples collected during ARCS demonstration
  22. Enrichment Factors for PCBs in feed, fines, particulate organics and washed sand
  23. Enrichment Factors for metals in feed, fines, particulate organics and sand
  24. Distribution of treatment cost for 10,000 and 100,000 cubic yard estimates
  25. Comparison of % sub-53 material in feed and washed sand
  26. Comparison of total organic carbon content of feed and washed sand
  27. Comparison of PCB concentrations in feed and washed sand
  28. Summary of percentage of fines, total organic carbon, and dry density found in process streams


  1. Modes of operation used during Saginaw Pilot- Scale Demonstration
  2. Cost of Sediment Washing Pilot-Scale Demonstration at Saginaw
  3. Summary of ARCS sampling of the Bergmann USA process
  4. Analytical parameters for sediment samples (modified from QAPP)
  5. Analytical parameters for water samples (modified from QAPP)
  6. Estimates by weight of input and output streams
  7. Overall physical separation achieved
  8. Physical separation achieved by Hydrocyclone Separator 1
  9. Physical separation achieved by Dense Media Separator (DMS)
  10. Dense Media Separator underflow (Station 11) comparison at two settings
  11. Dense Media Separator overflow (Station 10) before and after change in sampling location
  12. Grain size distribution of Attrition Scrubber feed and discharge streams
  13. Grain size distribution of Hydrocyclone Number 2 feed and discharge streams
  14. Grain size distribution of Hydrocyclone No 3. when No. 2 is bypassed
  15. Grain size distribution of Hydrocyclone No. 3 when No. 2 is operating
  16. Grain size separation achieved by Sand Recovery Screen
  17. Split Deck Dewatering Screen input and output
  18. PCB concentrations in process input and output streams
  19. Bench scale derived enrichment factors for metals and PCBs in various grain size groupings
  20. Summary of metals data from ARCS Pilot-Scale Demonstration
  21. Cost estimates and % of total costs for remediating 10,000 and 100,000 cubic yards of Saginaw River sediments at 50 tons per hour
  22. Average removal levels for individual materials when comparing feed with washed sand



AOC--Area of Concern
ARCS--Assessment and Remediation of Contaminated Sediments
CDF--Confined Disposal Facility
COE--U.S. Army Corps of Engineers
CSO--Combined Sewer Overflow
cy--cubic yard
DMS--Dense Media Separator
EA--Environmental Assessment
ECMPDR--East Central Michigan Planning and Development Region
EIS--Environmental Impact Statement
ETWG--Engineering/Technology Work Group
FONSI--Finding of No Significant Impact
fpm--feet per minute
FWS--Fish and Wildlife Service of U.S. Dept. of Interior
GLNPO--Great Lakes National Program Office of USEPA
gpm--gallons per minute
IJC --International Joint Commission
lbs/hr--pounds per hour
LWD--Low Water Datum
MDNR--Michigan Department of Natural Resources
mg/kg--milligram per kilogram
MSU--Michigan State University
NEPA--National Environmental Policy Act
ng/g--nanogram per gram
O+G--oil and grease
PAH--polynuclear aromatic hydrocarbon
PCB--polychlorinated biphenyl
PBB--polybrominated biphenyl
ppb--part per billion
ppm--part per million
psi--pounds per square inch
PVC--polyvinyl chloride
QAPP--Quality Assurance Project Plan
RAP--Remedial Action Plan
RCRA--Resource Conservation and Recovery Act
rpm--revolutions per minute
SAIC--Science Applications International Corporation
SCS--Soil Conservation Service
SCD--Soil Conservation District
SITE--Superfund Innovative Technology Evaluation
TMA/ERG--Thermo Analytical Inc./Environmental Research Group
TOC--total organic carbon
tph--tons per hour
TSCA--Toxic Substances Control Act
TSS--total suspended solids
TVS--total volatile solids
USDA--United States Department of Agriculture
USEPA--United States Environmental Protection Agency
WES--Waterways Experiment Station of COE
WWTP--Waste Water Treatment Plant
g/g--microgram per gram
g/kg--microgram per kilogram
g/l--microgram per liter




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