Publication Summary

This briefing paper summarizes water quality studies conducted in Water Resource Inventory Area (WRIA) TIS2, the San Juan Islands, by the Environmental Investigations and Laboratory Services Program of the Washington State Department of Ecology.

This briefing paper summarizes water quality studies conducted in Water Resource Inventory Area (WRIA) TIS2, the San Juan Islands, by the Environmental Investigations and Laboratory Services Program of the Washington State Department of Ecology.

The open marine waters of the San Juan Islands, located at the intersection of the Strait of Juan de Fuca and the Strait of Georgia, are well flushed (strong currents, deep channels, tidal mixing). The islands are drained by a number of small, mostly unnamed streams with drainage areas generally less than five square miles. Streams typically are dry in the summer. Numerous small lakes, ponds, pits and reservoirs occur on the islands and are sources of water for drinking, stock watering and irrigation. Ground water provides most of the drinking water in the islands. Productive sand and gravel aquifers exist on Lopez Island but most wells obtain water from less productive bedrock aquifers.

Eight dischargers, seven municipal and one industrial, operate with National Pollutant Discharge Elimination System (NPDES) permits.

The proposed 1996 Section 303(d) List Decision Matrix identifies five impaired marine water bodies. The water bodies are listed for excursions of the following parameters (number of listings are in parentheses): temperature (5), dissolved oxygen (5), pH (3), fecal coliform (3) and ammonia-N (1). All listings with the exception of one, dissolved oxygen at Eastsound, are proposed for removal from the list.