EVALUATION OF ENVIRONMENTAL MONITORING DATA GATHERED DURING ASHTABULA RIVER DREDGING, ASHTABULA RIVER, OHIO

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1 EVALUATION OF ENVIRONMENTAL MONITORING DATA GATHERED DURING ASHTABULA RIVER DREDGING, ASHTABULA RIVER, OHIO D. Plomb 1, S. Cieniawski 2, and D. Pham 3 ABSTRACT The Ashtabula River Area of Concern (AOC) lies in extreme northeast Ohio. The sediments within the Ashtabula River AOC are contaminated with polychlorinated biphenyls (PCBs) and radionuclides. PCBs are the primary constituent of concern. Based on previous evaluations of the site and collaboration between the various stakeholder groups, a dredging and disposal remedy was selected for the contaminated sediments in the Ashtabula River between the Upper Turning Basin and the 5th Street Bridge (Figure 1). The immediate project goals were to remove as much contaminant mass as feasible given constructability and financial constraints, and to restore navigational use of the river. Long-term reductions in surficial PCB concentrations are anticipated as a result of the completed environmental dredging project and natural sedimentation of clean sediments in the project area. Between 2006 and 2007, approximately 382,000 cubic meters (500,000 cubic yards) of sediment were dredged from the AOC. A 15-centimeter (6-inch) sand cover was also placed over designated areas following the completion of dredging activities. The remedial action (RA) was conducted on behalf of the U.S. Environmental Protection Agency (USEPA) under the Great Lakes Legacy Act (GLLA). One of the key components of the RA was environmental monitoring of the Ashtabula River to ensure protection of human health and the environment during dredging operations. The environmental monitoring activities included monitoring the water quality for excessive sediment resuspension during dredging, quantifying PCB and radionuclide levels in the water column during dredging, characterizing the thickness of the remaining sediment column and surficial PCB concentrations following completion of dredging, and conducting bathymetric surveys following completion of dredging and sand cover placement. As noted, one of the environmental monitoring components was to monitor sediment conditions following removal activities to ensure that the horizontal and vertical limits of dredging were achieved and that no high levels of contamination were left exposed. Characterization of post-dredge sediment conditions was accomplished by conducting a post-dredge bathymetric survey as well as by measuring post-dredge sediment thicknesses through probing and by collecting post-dredge surface sediment samples. Using the post-dredge surface sediment data, a post-dredge surface-weighted average concentration (SWAC) was calculated to determine the average PCB concentration remaining following dredging. The PCB SWAC was calculated to be 2.4 parts per million (ppm) for the entire dredge area prior to sand placement. Following sand placement over designated areas, the PCB SWAC was reduced to 1.1 ppm for the entire dredge area. A cleanup pass was performed at approximately 20% of the post-dredge sediment sampling locations. Segregating the cleanup areas from the non-cleanup areas, a PCB SWAC was also calculated. The PCB SWAC for cleanup areas was calculated to be 0.1 ppm. The PCB SWAC for non-cleanup areas was calculated to be 3.9 ppm. These values are prior to sand cover placement. Keywords: Contaminated sediment, PCBs, radionuclides, SWAC, survey. 1 Senior Project Manager, CH2M HILL, 135 S. 84 th St., Suite 325, Milwaukee, WI, 53214, USA, T: , dplomb@ch2m.com 2 Work Assignment Manager, U.S. EPA Region 5, Great Lakes National Program Office (GLNPO), 77 W. Jackson Blvd., Chicago, IL 60604, USA, T: , cieniawski.scott@epa.gov 3 Project Scientist, CH2M HILL, 135 S. 84 th St., Suite 325, Milwaukee, WI, 53214, USA, T: , dpham@ch2m.com 329

2 0 600 Feet Legend Project Area Figure 1 - Ashtabula River RA Project Area - Ashtabula River AOC 330

3 INTRODUCTION The Ashtabula River Area of Concern (AOC) lies in extreme northeast Ohio. The sediments within the Ashtabula River AOC are contaminated with polychlorinated biphenyls (PCBs) and radionuclides. The maximum historical PCB concentration was 660 parts per million (ppm), with an average of 7.5 ppm throughout the sediment column (Ashtabula River Partnership, 2001). PCBs are the primary constituent of concern. Based on previous evaluations of the site and collaboration between the various stakeholder groups, a dredging and disposal remedy was selected for the contaminated sediments in the Ashtabula River between the Upper Turning Basin and the 5th Street Bridge (Figure 1). The project goals were to remove as much contaminant mass as feasible given constructability and financial constraints, and to restore navigational use of the river. The main components of the remedial action (RA) activities were: 1) environmental dredging of contaminated sediments from just south of the Upper Turning Basin to the 5th Street Bridge, 2) monitoring of dredging conditions during removal activities to ensure that the horizontal and vertical limits of dredging are achieved and no high levels of contamination are left exposed, and the protection of human health and the environment is ensured during the dredging process, and 3) manual placement of clean cover material over specific areas. The RA was conducted on behalf of the U.S. Environmental Protection Agency (USEPA) under the Great Lakes Legacy Act (GLLA). DREDGING AND SAND COVER ACTIVITIES Between 2006 and 2007, approximately 382,000 cubic meters (500,000 cubic yards) of sediment were dredged from the AOC. The dredged sediments were transported hydraulically through a dual-walled high-density polyethylene (HDPE) pipeline to a consolidation facility (CF) where they were passively dewatered in geotextile tubes, and the weep water returned to the Ashtabula River after being treated at the water treatment plant (WTP). The sediments containing geotextile tubes will remain in place at the CF, which is a specially constructed Toxic Substances Control Act (TSCA)-level facility. Dredging operations were completed in mid-october Following the completion of dredging, placement of clean cover material occurred over specified areas. Two areas received cover material, encompassing an area of approximately 9,160 square meters (98,600 square feet) (DMU-12 and the North slope of Jack s Marine). A 15- centimeter (6-inch) sand cover was placed over these designated areas. ENVIRONMENTAL MONITORING ACTIVITIES One of the key components of the RA was environmental monitoring of the Ashtabula River to ensure protection of human health and the environment during dredging operations. The environmental monitoring activities included monitoring the water quality for excessive sediment resuspension during dredging, quantifying PCB and radionuclide levels in the water column during dredging, characterizing the thickness of the remaining sediment column and surficial PCB concentrations following completion of dredging, and conducting bathymetric surveys following completion of dredging and sand cover placement. Monitoring of Water Quality for Turbidity/Total Suspended Solids Water quality monitoring was accomplished through turbidity monitoring as a means to monitor and control contaminant release and resuspension during dredging operations. Three locations along the river were monitored for turbidity by measuring nephelometric turbidity units (NTUs). A correlation of turbidity to total suspended solids (TSS) was developed during 2006 dredging activities to estimate TSS concentrations using the turbidity readings as a surrogate. TSS concentrations were determined using turbidity as a surrogate based on an established correlation between turbidity levels and TSS concentrations derived during the 2006 dredging season. The formula for conversion of turbidity to TSS is: TSS (mg/l) = [ * (Turbidity in NTU)] The turbidity-tss correlation equation was based on data, as presented below. 331

4 End of 2006 Turbidity-TSS Correlation y = x R 2 = TSS (mg/l) Turbidity (NTU) Turbidity monitoring was conducted continuously during dredging operations. The monitoring buoys were located at US-1 (upstream location), DS-1 (downstream location), and RM-1 (river mouth location). The US-1 location was located upstream of the site, adjacent to the ARU Campground. The DS-1 location was located approximately 213 meters (700 feet) downstream of the 2007 dredging area and moved accordingly as dredging progressed down the river. The RM-1 location was located between the 5th Street Bridge and the river mouth. At each location, turbidity was recorded typically every 15 minutes by measuring NTUs by way of a turbidity meter at one-half the water column depth at that location. Dredging operations were to be performed in such a manner as to prevent excessive sediment resuspension based on TSS concentration measurements (or NTUs). For the purposes of the Ashtabula River dredging project, excessive resuspension was defined as exceeding a TSS concentration of 50 milligrams per liter (mg/l) above a daily background (upstream) concentration within 213 meters (700 feet) of the dredge head (measured on the downstream side according to the prevailing water flow conditions) at one-half the water column depth. This 50 mg/l TSS criteria was based on a 4-hour rolling average of TSS measurements. Only periodic exceedances of the 25 mg/l TSS warning level and the 50 mg/l TSS action level were observed during dredging at brief intervals at the DS-1 (213 meters downstream) location. Exceedances were immediately relayed to the dredge crew. The reason for the exceedance(s) was investigated and corrective actions, if required, were instigated. The exceedances were summarized in the daily and weekly reports for their respective periods. Water Column Sampling Water column sampling was conducted to provide historical data relative to PCB and radionuclide concentrations in the water column before and during dredging operations. Two locations along the river were sampled on a weekly basis for PCBs, Radium-226 (Ra-226), Radium-228 (Ra-228), total uranium (U), and TSS. The water sampling locations were at (1) a fixed background location upstream of the dredging operations at onehalf the water column depth and (2) a location downstream of the project dredging area near the mouth of the Ashtabula River at one-half the water column depth. The upstream sampling location was the same location as the US-1 turbidity monitoring location. The downstream location was the same location as the RM-1 turbidity monitoring location. Radioisotope concentrations in the water column during dredging were detected at low concentrations or at concentrations similar to those detected in the water column prior to dredging operations commenced in PCBs were consistently not detected in the water column during dredging in both 2006 and

5 Post-dredge Sediment Characterization One of the environmental monitoring components was to monitor of sediment conditions following removal activities to ensure that the horizontal and vertical limits of dredging were achieved and that no high levels of contamination were left exposed. Characterization of post-dredge sediment conditions was accomplished by conducting a post-dredge bathymetric survey as well as by measuring post-dredge sediment thicknesses through probing and by collecting post-dredge surface sediment samples. Post-dredge surface sediment samples were analyzed for PCBs. PCB concentrations ranged from nondetects to 32 ppm, with an average of 2.5 ppm (Figure 2). Using the post-dredge surface sediment data, a post-dredge surfaceweighted average concentration (SWAC) was calculated to determine the average PCB concentration remaining following dredging. The PCB SWAC was calculated to be 2.4 ppm for the entire dredge area prior to sand placement. Following sand placement over designated areas, the PCB SWAC was reduced to 1.1 ppm for the entire dredge area. A cleanup pass was performed at approximately 20% of the post-dredge sediment sampling locations. Segregating the cleanup areas from the non-cleanup areas, a PCB SWAC was also calculated. The PCB SWAC for cleanup areas was calculated to be 0.1 ppm. The PCB SWAC for non-cleanup areas was calculated to be 3.9 ppm. These values are prior to sand cover placement. CONCLUSIONS Dredging of bottom sediments within the Ashtabula River was successfully conducted, reducing contaminant mass within the Ashtabula River system. Environmental monitoring of river conditions before, during, and after removal activities were conducted which ensured that the horizontal and vertical limits of dredging were achieved and no high levels of contamination were left exposed. The environmental monitoring also ensured the protection of human health and the environment during the dredging activities. REFERENCES Ashtabula River Partnership (2001). Final Comprehensive Management Plan, Ashtabula River & Harbor, Ashtabula, Ohio. Disclaimer: The contents of this paper do not constitute official U.S. EPA opinion or policy. Mention of business or products does not constitute endorsement by U.S. EPA or its employees. 333

6 0 600 Feet Legend Surface Sediment Sampling Locations Dredge Area PCB Sample Results (mg/kg) > Figure 2 - Ashtabula River Post-Dredge Sediment Verification PCB Sample Results - Ashtabula River AOC 334