Appraisal of ground-water conditions and potential for seawater intrusion at Taholah, Quinault Indian Reservation, Washington

Several wells drilled to supplement the spring-fed water supply of the town of Taholah, in the Quinault River Valley, Washington , yielded water with chloride concentrations greater than 300 milligrams/L. Therefore, a study was conducted to define the movement and quality of the groundwater system at Taholah and at alternative well sites in adjacent areas. Results showed that during low tide, groundwater flows from Taholah northward to the river and westward to the ocean. During high tide water flows into the groundwater system along all margins of Taholah, causing a mounding of the underlying water table; the only outflow is seaward, probably at a depth of 60 to 75 ft below sea level. Marine water moves as far as 1.5 up the Quinault River during periods of combined high and low streamflow, and 0.5 mi during high tide and moderate streamflow, introducing large quantities of salty water into groundwater system and precluding its use as a water supply source. Unconsolidated glacial deposits and underlying Tertiary siltstones southeast of Taholah are not an adequate source for the community 's water needs. However, coarse-grained unconsolidated materials lying farther east along the Quinault River may be capable of supplying the anticipated need of about 300 gallons/min. (USGS)