Reports
Cox Creek Dredge Material Containment Facility exterior monitoring: sedimentary environment 2008
2009, Hill, J.M.; Van Ryswick, S.; Wells, D.V.
File Reports, Coastal and Estuarine Geology, File Report 2009-07
Abstract
The Cox Creek site is a dredged material containment facility (DMCF) located in Baltimore Harbor. The Cox Creek DMCF is a site which was in operation in the 1960’s through 1984, which has been reactivated. A limited amount of material was accepted in 2005 – 2008. The site is an upland disposal site anchored to land, with a diked containment area projecting into the Harbor. Dredged material from Baltimore Harbor is the primary material designated for placement at the site. Use of the site will prevent overboard disposal of dredged sediment and accept material that would in the past be sent to the Hart-Miller Island Dredge Material Containment Facility (HMI DMCF). HMI DMCF is to be closed at the end of 2009.
A total of 10 sites were sampled to monitor the effects of reactivation and operation of the containment facility. Nine (9) monitoring sites adjacent to the area with 1 site designated as reference site. EA Engineering, Science and Technology (EA) collected the samples and the Maryland Geological Survey (MGS) was responsible for analyses and interpretation of the data. The samples were collected September 23 & 24, 2008. Samples consisted of undisturbed sediments collected at the sediment-water interface.
The data showed:
- Sediments are generally fine grained with a gradient of higher sand content close to the dike, sand content diminishing away from the dike toward the channel.
- Based on the total nitrogen (N) content of the sediment, the Cox Creek DMCF study area has a greater terrigenous carbon (C) input compared to input from primary production.
- The sulfur to carbon (S:C) ratio is lower than further into the harbor indicating that the area is slightly more disturbed or has a higher sedimentation rate than further into the Harbor.
- In monitoring years 2006 and 2007 cadmium (Cd), manganese (Mn), nickel (Ni) and 25% of the zinc (Zn) sites were within background levels found for the Northern Chesapeake Bay. The number of samples and the number of elements within background levels increased in year 2008: Cd, Mn, and Ni, remained at background; the number of sites for Zn increased from 25% to 70%, and chromium (Cr) and copper (Cu) had samples within background.
- Target metals in the study areas follow the general pattern seen in the 1994 - 1997 Baltimore Harbor study. Site specific variations at the Cox Creek DMCF appear to be a strong source of iron (Fe) and lead (Pb), and a lesser source of Cr, Cu and Zn to the external sedimentary environment.
- The levels from the dike are comparable to enrichment levels found in that part of the Harbor.
- The reference site is not representative of the area. Both physically and chemically the site is not representative of the DMCF. This monitoring year the greatest variation occurred at the reference site; for example the % sand dropped more than 50% (greater than 60% in 2007 to less than 10% in 2008) and the clay to mud ration (CMR) increased more than 20%
- General distribution patterns and concentrations are comparable for all three monitoring years indicating effects from the operations of the DMCF are not significantly altering the exterior environment.
