HECO annually conducts and reports results of a biological monitoring program for waters receiving effluent from the Kahe Generating Station, O'ahu, Hawai'i from 1977 to 1996 (NCEI Accession 9900012)

The volume of sand and silt entrained and circulated by operation of the Kahe Generating Station is an environmental parameter of considerable geological and biological importance. Wave-suspended sediments are carried in cooling water through the station's condensers and discharged from the station's outfall. Sediment entrainment represents a potential loss of sand from the littoral system which consequently affects the supply of sand available to maintain beach configurations in the area. Biologically, deposition of entrained sand off the outfall and the distribution of silt suspended in the thermal plume represent potential stressors for benthic (bottom-dwelling) organisms, which may have no mechanisms for ridding themselves of sediments, or must expend energy to do so. Burial of hard reef surfaces by sand and silt diminishes the surface area available for recruitment of sessile benthic organisms and eliminates habitat of motile benthos and demersal fishes.

HECO has monitored sediment entrainment and throughput related to the station's circulating cooling water system since 1977. The startup of Kahe Unit 6 resulted in a noticeable increase of annual sediment entrainment rates. However, Hurricane Iwa reduced sand levels along the entire Kahe reef front in late 1982, and sediment entrainment values have been steadily declining since. This is because less sand has been available near the intake to be entrained. The following study presents the eighteenth year of sediment entrainment monitoring with six Kahe units in operation.