Kalamazoo River Time-Integrated Sediment Sampling

摘要

Background/Objectives. The mobility and transport of crude oil in a riverine system istypically influenced by oil physical properties. Submerged oil is often associated withorganic and/or fine-grained deposits in the near surface sediment profile. An estimated840,000 gallons of crude oil were released near Marshall, Michigan on July 26, 2010,from a rupture in Enbridge Energy Line 6B. Oil removal in the Kalamazoo River was initiatedafter the release and has continued through 2012. The oil recovery work wasinitially focused on overbank areas, but was expanded when submerged oil was identifiedin some river areas that extended for up to 40 miles from the release. Time-integratedsediment samplers were placed at selected locations throughout the Kalamazoo River toassess potential for submerged oil transport in suspended sediment.Approach/Activities. The samplers were installed to characterize the suspended sedimentparticle size distribution and associated total petroleum hydrocarbon (TPH) andpolycyclic aromatic hydrocarbon (PAH) concentrations from selected locations. Samplerswere installed in the river above and below the oil release to compare background anddownstream river conditions. The main body of the sampler is a 4 inch inside diameter(ID) polyvinyl chloride pipe of about 39 inch length. Semi-rigid inlet and outlet tubes ofabout 0.16 inch ID are located at each end of the sampler main body. The sampler is designedto capture fine-grained sediment using ambient flow to induce settling in thesampler body due to a flow velocity reduction. The sampler was selected because it provideda cost effective method to obtain representative suspended sediment samples thatare influenced by eposodic transport. The design and operating principles of the samplerare described by Phillips et al. (2000). The samplers were installed at 20 locations in theKalamazoo River. At each location two samplers were installed at two depths from thewater surface. One sampler was installed 6 to 20 inches above the channel bed. A secondsampler was installed to a depth from the water surface of about 33 percent of the totalwater column when the water depth was greater than 2.5 feet. Samplers were in place forabout one month in the fall of 2011 and a several month period in the summer of 2012.Results/Lessons Learned. Suspended sediment TPH concentrations from samples obtainedin 2011 above the source release were similar to those from downriver samples.These results were consistent with the results from core sediment samples collected frombackground and submerged oil depositional locations. These analyses indicate that TPHdoes not provide a reliable basis for characterizing sediment submerged oil impact presumablydue to interferences associated with natural organics and other TPH sources.Particle size distribution was not conducted on samples obtained in 2011 since the onemonth collection period was not sufficient to collect the required suspended sediment