For the
Assessment and Remediation of Contaminated Sediments
(ARCS) Program
U.S. Environmental Protection Agency
Great Lakes National Program Office
Chicago, Illinois
Acknowledgements ii
Disclaimer iii
Abstract iv
List of Figures viii
List of Tables x
List of Abbreviations and Symbols xii
1 Five Areas of Concern designated for on-site ARCS Pilot-Scale Demonstrations 2
2 Major tributaries to Saginaw Bay 4
3 Location of the Saginaw River/Bay Area of Concern 4
4 Location of dredging and processing areas 10
5 Layout of Pilot-Scale Demonstration site for sediment washing at Saginaw Bay, MI 13
6 Feed hopper and conveyors, and sand discharge conveyor 15
7 General process flow diagram for the Bergmann USA system used at Saginaw Bay 17
8 Barge-mounted Bergmann USA sediment washing plant at Saginaw Confined Disposal Area 18
9 Rotary Trommel showing headbox, upper washing zone, and lower sizing zone 19
10 Hydrocyclone Separator Number 1, mounted above the Dense Media Separator 19
11 Schematic of a Linatex Hydrocyclone Separator 21
12 Schematic of Linatex Dense Media Separator 22
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 24
14 Clarifier used during Spring 1992 operations 24
15 Sampling points for ARCS Pilot-Scale Demonstration at Saginaw Bay 34
16 Procedure No. 1, particle sizing less than 38 microns 35
17 Procedure No. 2, particle sizing greater than 38 microns 35
18 Grain size distribution of feed 42
19 Grain size distribution of four discharge streams 43
20 Enrichment Factors for TOC in feed, fines, particulate organics and washed sand 44
21 PCB concentrations of 4 hour composite samples collected during ARCS demonstration 65
22 Enrichment Factors for PCBs in feed, fines, particulate organics and washed sand 65
23 Enrichment Factors for metals in feed, fines, particulate organics and sand 69
24 Distribution of treatment cost for 10,000 and 100,000 cubic yard estimates 74
25 Comparison of % sub-53µ material in feed and washed sand 78
26 Comparison of total organic carbon content of feed and washed sand 79
27 Comparison of PCB concentrations in feed and washed sand 80
28 Summary of percentage of fines, total organic carbon, and dry density found in process streams 82
1 Modes of operation used during Saginaw Pilot- Scale Demonstration 27
2 Cost of Sediment Washing Pilot-Scale Demonstration at Saginaw 30
3 Summary of ARCS sampling of the Bergmann USA process 32
4 Analytical parameters for sediment samples (modified from QAPP) 36
5 Analytical parameters for water samples (modified from QAPP) 37
6 Estimates by weight of input and output streams 39
7 Overall physical separation achieved 41
8 Physical separation achieved by Hydrocyclone Separator 1 46
9 Physical separation achieved by Dense Media Separator (DMS) 48
10 Dense Media Separator underflow (Station 11) comparison at two settings 49
11 Dense Media Separator overflow (Station 10) before and after change in sampling location 51
12 Grain size distribution of Attrition Scrubber feed and discharge streams 52
13 Grain size distribution of Hydrocyclone Number 2 feed and discharge streams 54
14 Grain size distribution of Hydrocyclone No 3. when No. 2 is bypassed 55
15 Grain size distribution of Hydrocyclone No. 3 when No. 2 is operating 57
16 Grain size separation achieved by Sand Recovery Screen 58
17 Split Deck Dewatering Screen input and output 60
18 PCB concentrations in process input and output streams 63
19 Bench scale derived enrichment factors for metals and PCBs in various grain size groupings 64
20 Summary of metals data from ARCS Pilot-Scale Demonstration 67
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 73
22 Average removal levels for individual materials when comparing feed with washed sand 77
ABBREVIATIONS
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
DDT--dichloro-diphenyl-trichloro-ethane
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
hp--Horsepower
IJC --International Joint Commission
lbs--pounds
lbs/hr--pounds per hour
LWD--Low Water Datum
MDNR--Michigan Department of Natural Resources
min--minute
mg--milligram
mg/kg--milligram per kilogram
mm--millimeter
MSU--Michigan State University
NEPA--National Environmental Policy Act
ng--nanogram
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
µ--micron
µg--microgram
µg/g--microgram per gram
µg/kg--microgram per kilogram
µg/l--microgram per liter
SYMBOLS
Cd--cadmium
Cr--chromium
Cu--copper
Hg--mercury
Ni--nickel
Pb--lead
Zn--zinc
%--percent
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.
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.
DESCRIPTION OF THE SAGINAW RIVER AND BAY AREA OF CONCERN
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.
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