USGS Washington Water Science Center
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WA402 - Water Resources of the Swinomish Indian Reservation - Completed FY1999
Problem - The Swinomish Indian Tribal Community (SITC) is interested in protecting the water resources of its reservation for the beneficial uses of the members of the Tribe. Protection from overuse and degradation of quality are the main areas of interest. Concerns have arisen that pumping of ground water has resulted in depleted stream flows and has caused seawater intrusion into parts of the Reservation. There is also concern that a landfill (household wastes and wood-processing wastes) may be contaminating the ground-water system. In order to effectively determine optimum future land use, the Tribe needs updated streamflow and ground-water water-quality data to enter into a water-resources data base.
Objectives - The purposes of this study are to:
WA358 - Hydrology of the Swinomish Indian Reservation, Northwestern Washington - Completed FY1998
Problem - A previous (1979) USGS investigation of the Swinomish Indian Reservation documented the existence of three shallow aquifers within the top 200-300 feet of a 900-foot assemblage of unconsolidated sediments beneath the Reservation. These three aquifers are an uppermost till unit, a middle unit of stratified drift, and a lower clay unit. At the time of that earlier investigation, all wells were finished in one of the three aquifer units and no well completely penetrated through the lower clay unit. Since 1979, several wells, including two public-supply wells, have penetrated the clay unit and a deeper aquifer has been encountered beneath the central part of the Reservation. The extent and hydraulic characteristics of this deeper aquifer are unknown.
In 1981 an inactive waste disposal site was discovered about a mile away from the Tribal well field. The site had been used for the disposal of refinery wastes and investigation by a private consultant indicated the presence of substantial amounts of polycyclic aromatic hydrocarbons (PAH's), and aliphatic hydrocarbons, as well as smaller concentrations of volatile organic compounds.
A better understanding of the Swinomish ground-water system and the potential and likelihood of its contamination by wastes from the disposal site are needed.
Objectives - The objectives of this study are to verify the existence of a deep aquifer and attempt to describe its extent, thickness, and hydraulic characteristics. We will also determine the flow directions of the "shallow" (upper three) aquifers and estimate the degree of interconnection between the shallow and deep aquifers.
Approach We will locate and collect data for all wells tapping the deep aquifer and use these, along with existing geologic maps, to determine the extent and thickness of the aquifer. Data for wells drilled in the shallow aquifer since our 1979 investigation will also be collected. We will measure static water levels in as many wells as possible to verify ground-water flow directions for the shallow aquifer and attempt to describe the ground-water flow directions in the deeper aquifer. We will estimate hydraulic conductivity and transmissivity of the deep aquifer and the degree of interconnection between the shallow and deep aquifers. We will compile a pumpage history for the Tribal well field using data from the 1979 study and Tribal records. A field reconnaissance of the waste-disposal site is also needed to determine its location, extent, physiography, and local conditions of surface-water runoff. Water quality samples will be collected from surface runoff at the site.
WA181 - Water Resources of the Swinomish Indian Reservation - Completed FY1979
Problem - The Swinomish Indians need a safe and reliable source of potable water for domestic use and for development of fisheries resources. Present sources are from off-reservation or from wells with limited yield. Many of these wells have problems with bacterial contamination, high iron content, or salt-water intrusion. Surface-water supplies are very scarce, so additional supplies must come primarily from ground water.
Objectives - Define the ground-water system underlying the Reservation in terms of quantity, quality, and location so that the Swinomish Tribal Senate will have the information necessary to properly develop, manage, and conserve this valuable resource and to evaluate the available surface water (both quantity and quality) in terms of fish rearing potential.
Approach All major existing wells will be inventoried, seismic refraction surveys will be made to determine aquifer thickness. Three test wells will be drilled and pumping tests conducted. An observation well network will be established and water from about 40 wells will be analyzed for chloride, iron, and coliform bacteria.