Most residential and industrial development of the Lower Kenai Peninsula, Alaska, is along the coast of Cook Inlet. Most of the information about subsurface conditions is obtained from wells along the coast. Ground water is recharged by local precipitation, and slow drainage of ground water to the streams maintains streamflow during winters and periods of no precipitation. Sedimentary bedrock of the Tertiary Kenai Group is the principal source of water to wells, but subsurface data are too sparse to differentiate individual aquifers within the bedrock. Most bedrock wells are completed in poorly consolidated sandstone. Glacial till overlies bedrock in much of the study area, but few wells obtain water from the poorly permeable till. Glacial outwash and abandoned-channel deposits in major drainageways of alluvial plains provide water to wells but are little utilized and have not been explored by drilling. Intermorainal valleys and areas of low relief are poorly drained , and bog deposits overlie surficial materials in parts of the area. Bog deposits contain highly colored, iron-rich water that is undesirable to most consumers. Lacustrine clays overlie and are interbedded with fluvial materials and contain little extractable water. Streams have incised older glacial sediments and deposited alluvium along the present flood plains. Where the alluvium is thick enough, it has good potential for providing ground water to high-capacity wells. However, production of ground water from alluvium or other deposits hydraulically connected to streams will reduce streamflow. Surficial deposits with the best potential for developing significant ground-water supplies in the study area are the deltaic complex near the mouth of Kasilof River, the alluvium of Crooked Creek, and abandoned-channel deposits in the alluvial plain near Ninilchik and in an ancestral drainageway of Tustumena Glacier south of Crooked Creek. (USGS)