Reports
Centreville Dam Sediments Study Queen Anne's County, Maryland. Reconnaissance Survey of Sediments At Centreville Dam, Corsica River
2014, Van Ryswick, S., Sylvia, E.R.
File Reports, Coastal and Estuarine Geology, File Report 14-01
Executive Summary
In response to a request by American Rivers, Maryland Geological Survey (MGS) was contracted to study the sediments within the Centreville Dam impoundment located in Queen Anne’s County in the State of Maryland. The dam is located at the head of Gravel Run immediately to the southeast of the Rt. 213 bridge. The sediments required TCLP analysis to verify that the sediments meet the regulatory thresholds for TCLP metals for disposal at the Queen Anne's County landfill. Cores were collected at six locations to quantify the physical and chemical properties of the sediment, and to test for the presence of leachable metals above regulatory thresholds. The samples tested included sediments from five sites above the dam, a composite sample from these five sites, and a sample from a site below the dam for comparison. The fieldwork for this study occurred in September 2013.
The physical properties of the sediments accumulated behind Centreville Dam were dominated by sandy mud that was unconsolidated near the surface with increased consolidation at depth. The underlying sediments contained increased sand and gravel with episodic laminations indicative of the pre-dam streambed as well as peaty deposits indicative of the predam marsh. The elemental analysis results were within the ranges expected for the sediments in the study area. The total background concentrations of arsenic, chromium and lead were all comparable to those recorded in similar studies with sample sites in Maryland (Vosnakis et al., 2009; Smith et al., 2013).
The TCLP analyses showed non-detectable concentrations of all TCLP metals for all samples tested. Due to non-detection, no differences in leachable metals concentrations were found between the sites above the dam and the site below the dam. The analysis of samples from five sites above the dam exceeds the mandate of four samples from various locations within the deposit. The composite sample tested to measure the average leachable metals from all sample sites above the dam also resulted in non-detection for all TCLP metals.
Based on the TCLP metals analyses of core samples collected for this study, the sediments located behind Centreville Dam do not contain any leachable metals concentrations above the regulatory thresholds. Therefore, the accumulated sediments behind the dam meet the regulatory requirements for placement in the Queen Anne's County landfill.
