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Bottom material from the Willamette River was collected and mixed with Willamette and Columbia River waters on May 17, 1977. The elutriate, as well as each sample, was analyzed for selected nutrients, metals, and pesticides. Results show that the average dissolved ammonia, manganese, and zinc concentrations would require dilution by receiving water to achieve aquatic-life criteria levels. INTRODUCTION On May 17, 1977, the U.S. Geological Survey, in cooperation with the U.S. Army Corps of Engineers (Corps), made an elutriate test. The test provided data for evaluating possible environmental effects of a Corps-proposed pilot dredging study for the off-channel disposal of Portland Harbor bottom material into the Columbia River. In the pilot study, the Corps would dredge material from the bottom of the Willamette River near RM (river mile) 9.2, load it onto a hopper barge with water-sediment overflow, and transport and dump it into the Columbia River. The National Marine Fisheries Service feels that the disposal operation would be economically feasible and that the nutrient-enriched dredging material might stimulate biological productivity in the Columbia River system. On February 1, 1977, a sample of Willamette River bottom material was collected at RM 9.2 and analyzed for chemicals that could adversely affect Columbia River aquatic life. On March 28, 1977, the preliminary chemical analyses were reviewed by personnel from the Corps of Engineers Navigational Division, National Marine Fisheries Service, and the U.S. Geological Survey. The U.S. Environmental Protection Agency later reviewed the data (McKenzie, 1977) and suggested that an elutriate study be made. The U.S. Environmental Protection Agency (1975, p. 41295) defines an elutriate as "the supernatant resulting from the vigorous 30-minute shaking of one part bottom sediment from the dredging site with four parts water (Vol/Vol) collected from the dredging site followed by one hour settling time and appropriate centrifugation and a 0.45-micron filtration." The elutriate test would indicate the chemicals in the bottom material that would dissolve into water during the dredging operation and possibly be toxic to aquatic life. During the proposed dredging operation, harbor bottom material would come in contact with Willamette River water through hopper overflow and with Columbia River water during the dumping operation. Sample analyses, therefore, included the following: One analysis of the bottom material, duplicate analyses of both Columbia and Willamette River water, and duplicate analyses of both bottom material-Willamette River water elutriate and bottom materialColumbia River water elutriate. SAMPLE COLLECTION The collection, preparation, and analysis of the river water, bottom material, and elutriate samples are described below. River Water A Willamette River water sample and a Columbia River water sample were collected from 1-meter depth at the proposed dredging site (Willamette River mile 9.2) and disposal site (Columbia River mile 101.8, near Kelley Point), respectively. The Willamette water sample was taken midchannel, and the Columbia water sample was taken about 300 feet from the south bank. After collection, the samples were stored in glass containers. Representative portions of each sample were independently filtered through prerinsed acidsoaked 0.45-micron membrane filters. The filtrate for a water sample was split into subsamples A and B and independently analyzed for pesticides, dissolved metals, cyanide, and ammonia using methods outlined by Goerlitz and Brown (1972) and Brown, Skougstad, and Fishman (1970). The remainder of each unfiltered water sample was used for the preparation of the respective elutriates. Bottom Material The Willamette River bottom material was collected at RM 9.2 using a Teflon-coated Ekman grab sampler. About 15 grab samples were collected from the bottom at midchannel and composited. The composite sample was mixed well and a portion was analyzed for chemical constituents using methods outlined by the U.S. Environmental Protection Agency (1974). Five representative portions (5 milliliters per portion) of the composited bed sample were each analyzed for percent moisture and residue, loss on ignition. The remainder of the bottom material was used in the elutriate test. ELUTRIATE TEST PROCEDURE The bottom material and river-water samples were mixed together in a volumetric sediment-to-water ratio of 1:4. For the purpose of simulating a dredging and disposal process, a 1:4 ratio is used to approximate a dredged material slurry (U.S. Army Corps of Engineers Waterways Expt. Sta., 1976). The mixture was placed in a glass carboy and mechanically mixed with a Teflon-coated stirrer for 30 minutes. After mixing, the suspension was allowed to settle for 1 hour. The supernatant was then decanted, centrifuged, and filtered through prerinsed 0.45-micron filters. Each filtrate (the standard elutriate) was then split into subsamples A and B, and each was analyzed for dissolved constituents using methods outlined by Goerlitz and Brown (1972) and Brown, Skougstad, and Fishman (1970). The elutriate test followed the general procedures outlined by the U.S. Army Corps of Engineers Waterways Experiment Station (1976). MOISTURE AND RESIDUE, LOSS ON IGNITION The percent moisture; density; and residue, loss on ignition, were analyzed on five subsamples of the bottom material collected for the elutriate test. The residue, loss on ignition, is the difference between the residue after evaporation and the residue after ignition. The densities were calculated from the determinations of moisture content of the bottom material. The analyses of percent moisture and residue, loss on ignition, were made as outlined by the American Public Health Association and others (1975).

Elutriation study of Willamette River bottom material and Willamette-Columbia River water