Hydrology for land-use planning: The Hillside area, Anchorage, Alaska

Abstract

Rapid residential growth of the Hillside area, Anchorage, Alaska, may cause depletion of aquifers and a change in quality of water resources as a result of extensive development of small-lot tracts. Ground-water yields are low and may be locally inadequate for single family requirements where wells produce from bedrock in the eastern Hillside region. At lower altitudes single family water requirements of 3 to 10 gallons per minute or 0.2 to 0.6 litre per second usually can be obtained, but aquifers capable of being pumped at larger yields for public supplies are uncommon. However, in a few localities, wells do produce 40 to 300 gallons per minute or 2.5 to 19 litres per second from sand and gravel aquifers lying within thick sequences of glacial till. Streamflow within the Hillside area is inadequate as a significant source of water for public supply. Springs, swamps, and water-logged surficial sediments in the Hillside area are mainly caused by hilly terrain and low permeability of surficial materials. The relative vulnerability of streams, lakes, and ground water to pollution caused by the discharge of liquid waste, particularly from onsite sewage-disposal systems, is moderate to high in about half the study area. At higher altitudes contamination of bedrock aquifers may occur if discharge of liquid wastes is not regulated. The deep sedimentary aquifers at lower altitudes are less susceptible to contamination. However, shallow groundwater bodies may become polluted by discharge of sewage effluent and, consequently, some deep wells may be contaminated by seepage down the outside of casings or through leaky casing joints and underground seals.