The SEIS Lands abut the ocean and are fronted by three distinct bays: Kawela Bay, Turtle Bay, and Kuilima Bay. Water quality in the area has been studied regularly for the past 20 years. The information from those studies will be combined with new surveys to document the existing water quality of the near-shore environment and to inventory the presence of marine biota, including endangered and threatened species. The results of these surveys will be included in the Draft supplemental environmental impact study (SEIS).
Kawela Bay is classified as Class A open coastal waters. Although the bay itself meets the physical criteria to be classified as an embayment it is not so classified in the State Standards. The normal water quality of Kawela Bay typically exceeds State Standard water quality criteria for either Open Coast or for an embayment. Recent surveys indicate no easily discernable changes in water quality along this coastline. Turbidity is a persistent problem, particularly in the eastern extreme of Kawela Bay, although the western portion of the bay often has water of excellent clarity. Water clarity in Kawela Bay is controlled by input of silt from the Kawela Stream and by the low water turnover rate in the right side of the bay. Turbidity is the result of a very low rate of water circulation over shallow reef flats, and is augmented by rare storm events that are responsible for supplying the bay with sediments that become trapped and easily re-suspended in the eastern section of the bay.
The bay is the recipient of a significant groundwater influx supplying high concentrations of both nitrogen and phosphorous to the bay. High levels of phosphorous are not typical in Hawaii and point to the unique nature of this condition in Kawela Bay. Phosphorous tends to be higher in the eastern portion of the bay, likely associated with the sediments and the longer residence time in this area. The relatively rich nutrient supply and shallow waters are doubtless responsible for the prolific algae growth and subsequent visitation by sea turtles which graze off these algae beds.
Oxygen content in the waters of the bay is usually excellent. However, during periods of high turbidity low oxygen levels in the eastern portion of the bay have been recorded.
A similar volume of surface flow enters the ocean at the East Main Drain and West Main Drain, as compared to the Kawela Stream volume. However, at both the East Main Drain and West Main Drain outlet locations, there is rapid mixing, dilution, and offshore transport of these waters. Nitrate plus nitrite levels follow this trend. At the West Main Drain, where near shore nitrate levels are often very high, the offshore (100 meter) measurements are typically low at background levels. Following a storm and flood event in March 1991, the reef off the East and West Main Drain outlets was free of silt within about one week. At Kawela Bay, however, it required about one year for the silt levels to return to pre-storm levels.
The Resort Master Plan includes rerouting Kawela Stream to the West Main Drain, effectively returning Kawela Stream to the approximate location of its historical channel. This change is anticipated to have a significant favorable impact on the water quality in Kawela Bay and no significant impact on the water quality in Turtle Bay since the latter has strong currents that will flush the sediment load out to sea. The replacement of the East Main Drain culvert outfall with an open channel design may result in an increase in sediment load on Kuilima Bay since water will flow more easily to the sea. This impact is not anticipated to be significant. Other possible impacts include water quality degradation resulting from short-term construction activities, and operational impacts pertaining to storm runoff and drainage control. These impacts are not anticipated to be significant because BMPs have been and will continue to be employed during operational activities and anticipated construction activities. Even though no significant adverse impacts are anticipated, the possibility of such impacts will be studied in the Draft SEIS.