Baseflow and Stormwater Contaminants in the Quinault, Queets, and Moclips River Tributaries

This collection of four companion child items documents water-quality conditions and hydrologic characteristics at stream monitoring sites in the Quinault, Queets, and Moclips River watersheds on the Olympic Peninsula of Washington State. Data were collected from May 2023, through December 2024, at up to seven sites on the Quinault Indian Reservation to support water-quality survey efforts and watershed evaluation. Continuous water level (depth) and water temperature time-series data were recorded at six sites from May 30, 2023 through December 5, 2024, at 15-minute intervals using paired HOBO U20L pressure transducer loggers. Water level data were barometrically corrected and processed through the USGS AQUARIUS Time-Series system. These records characterize the flow regime during passive sampler deployments and provide mean water temperatures used to select diffusion coefficients for trace-metal concentration calculations. Water level values represent relative measurements from an arbitrary reference point and are not absolute elevations.

Water and sediment grab samples were collected at six sites during low, late-summer flows from September 9 through September 24, 2024, prior to the onset of autumn storm events. Water samples were analyzed for trace metals (arsenic, cadmium, chromium, copper, lead, zinc), nutrients (nitrogen and phosphorus species), bacteria (fecal coliform, E. coli), dissolved organic carbon, chlorophyll a, turbidity, hardness, and total suspended solids. Sediment samples were sieved and analyzed for trace metals in the less-than-63-micrometer fraction, and for polycyclic aromatic hydrocarbons (PAHs), polybrominated diphenyl ethers (PBDEs), phthalates, and total organic carbon in the less-than-2-millimeter fraction. All analyses were performed by the Washington State Department of Ecology Manchester Environmental Laboratory.

Diffusive gradients in thin films (DGT) passive samplers were deployed at five sites from September 24 through December 5, 2024 to capture the first-flush response to autumn and early-winter storm events. Seventeen trace metals and metalloids were targeted: silver, aluminum, arsenic, cadmium, cobalt, chromium, copper, iron, manganese, molybdenum, nickel, lead, antimony, selenium, uranium, vanadium, and zinc. Estimated time-weighted mean water concentrations were calculated from accumulated mass on the binding resin using element-specific diffusion coefficients, sampler geometry, and deployment duration.

Semipermeable membrane devices (SPMDs) were deployed at six sites over the same September 24 through December 5, 2024, period (approximately 71 days) to assess PAH concentrations in surface waters during fall and early-winter storm events. Estimated ambient water concentrations were calculated from SPMD uptake data using performance reference compound (PRC)-derived sampling rates and the empirical uptake model. Together, these data provide measurements of trace metals, PAHs, nutrients, bacteria, organic contaminants, and hydrologic conditions in watersheds on the Quinault Indian Reservation.

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