Collection of sediments using a core sampler Upon arrival at a sampling site, the field crew determined if site conditions allowed a sediment sample collection (provided there were no concerns regarding access, personal safety, and availability of fine-grained sediment). The field sampling crew identified the proposed sampling location in the data sheets along with description of the physical characteristics of the site. The location initially was identified with a hand-held global positioning system (GPS) unit to identify the location for collection of sediment samples within a site. A boat (if used) was positioned near the sampling location within a site. Samples of sediment were collected from the reference site using a posthole digger (grab sampler) and sediment samples from the test sites were collected using 10-centimeter (cm) LexanŽ cores (core sampler). Equipment used to collect sediment was decontaminated between samples by brushing to remove sediment particles, washing with soapy water and rinsing with site water between collections of each set of samples. The following is a description of the procedure used to collect the composite sediment cores for a sampling location within a site: 1. At each sampling location, the lower section of a LexanŽ tube was placed on the top of the sediment and the depth of water was recorded. 2. The tube was driven into the sediment by hand until the targeted depth was achieved, or until refusal. The depth of penetration was recorded (from the sediment surface or depth from water surface and depth of water). 3. The tube was driven several more centimeters into the substrate, using a stainless-steel core driver to improve recovery of soft sediment. This procedure was done to obtain a section at the bottom of the core that helped prevent the loose sediment from escaping from the bottom of the tube. 4. A cap was placed on the top end of the tube to create a vacuum to help prevent the sediment plug from escaping from the bottom of the tube. 5. The tube was slowly pulled from the sediment, twisting slightly as removed (if necessary). 6. The integrity and depth of the core was recorded. If the core within the tube was not suitably intact, the sediment within the tube was discarded and a new sample was collected. 7. Keeping the tube upright, the sediment was extruded to the target sample depth into a 5-gallon high density polyethylene bucket. 8. The process was repeated until there was a minimum of 16 liters of sediment in two to three 5-gallon buckets for that composite sample of sediment. 9. Pore water was included in the samples of sediment and care was made to ensure that overlying water (that is, surface water) was not included in the samples to the extent practical. 10. The buckets containing the samples of sediment were then transported to a local staging building and were stored at 4 degrees Celsius) in the dark in a secured refrigeration truck.