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Sediment chemistry and characteristics of samples collected in 2019 from the Similkameen River above Enloe Dam, Okanogan County, Washington (ver. 3.0, March 2022)

May 20, 2022

This data release provides information on the chemistry and character of bed sediments accumulated in the 1.6-mile long impoundment behind Enloe Dam on the Similkameen River in Okanogan County, WA. Sediment samples were collected during four weeks in October – December 2019. The sampling locations were distributed among 10 transects that ranged from 0.1-0.2 miles apart along the length of the reservoir. Surficial grab samples of bed material were collected at 27 locations representing the left, right or center of the channel cross-section where sampling was possible using a Ponar sampler. Sediment cores were collected with a Vibracore at 12 locations at or near the surficial grab sample transects, and discrete sediment samples were selected from various depths below the sediment water interface from six of the cores collected. The deeper cores were collected using a telescoping system of 4, 2, and 1-inch aluminum cores liners. The maximum depth of sediment collected with the telescoping system was 35.9 feet below the sediment-water interface. At three sites samples of a sediment and water mixture (slurry-samples) were collected by pumping from the maximum depth of the two-inch core tube. Sediment samples were analyzed at AGAT Laboratories to determine the concentrations of 51 elements and at the USGS Pacific Coastal Marine Science Center for determination of grain size and carbon. Results of sample analyses are provided in four tables: Table-1 lists the location and element concentrations for 36 surficial bed material grab samples; Table-2 lists the location, maximum core depth, and element concentrations for 76 subsurface samples; Table-3 lists concentrations from carbon analysis (Total carbon, TC; Total inorganic carbon, TIC; and total organic carbon , TOC) for all surficial and core samples, and percent grain size (silt-clay, sand, gravel) for surficial samples only; Table-4 lists laboratory reported element concentrations for quality assurance/quality control samples with known element concentrations; Table 5 lists ratios of stable isotopes of carbon 13/12 and nitrogen 15/14, and total carbon and total nitrogen mass from select subsurface samples; Table 6 lists percent grain size (silt-clay, very fine sand, fine sand, medium sand, coarse sand) for select core samples; Table 7 lists the activity level of short-lived radionuclides for five slurry samples.

This dataset includes all samples from the original data release, plus an additional table of carbon and nitrogen isotope data, an additional table of percent grain size for core samples, and an additional table of radionuclides activities.

NOTE: While the previous versions is available from the author, all the records in the previous versions can be found in version 3.0.
First posted - March 12, 2021 (available from author)
Revised - December 17, 2021 (version 2.0)
Revised- March 14, 2022 (version 3.0)