Deep Confined to Semi-Confined Aquifer

Valley Aquifer: A confined to semi-confined aquifer exists at depths of up to 600 feet throughout the main trunk of the Upper Snoqualmie valley from Snoqualmie Falls upstream along the Middle and South Forks of the Snoqualmie River. This aquifer is tapped by wells drilled by the City of Snoqualmie and by several private wells in the vicinity of Tanner. This is the aquifer encountered in the EKCRWA test well in 1993. The aquifer is well defined in the Middle Fork/Tanner area and is overlain by a glacial till. It is also well defined between the City of Snoqualmie and Snoqualmie Falls, and is overlain by lacustrine materials and possibly till. The aquifer is not well defined in the vicinity of North Bend. Recent test drilling indicates that the till is absent in the vicinity of North Bend. Bedrock Aquifers: At least 43 wells in the upper basin obtain groundwater from bedrock, which is reported as sandstone, shale and basalt. Based on data presented by the USGS, these wells have static water levels that are fairly shallow relative to their depth, and have wide-ranging transmissivities. The bedrock, is therefore relatively productive in comparison to some bedrock aquifers.