| OCR Text |
Show Gray water contains soap, detergent, food waste in the form of small particles, and probably small amounts of other substances such as suntan oil, cooking oil, and toothpaste. The composition of these discharges has never been studied because it generally has been believed that the quantities are small and the substances non- polluting. ( Soaps act as emulsifiers and can be harmful to small organisms such as bacteria; but because the dilution factor for discharged gray water is tremendous, such effects are not likely to be measurable.) However, gray- water discharges are sometimes visible and have resulted in occasional public inquiries or critical comment on the nature of boat discharges. The growth of houseboat use could lead to a situation where a concentration of houseboats in a cove with little water circulation might render water locally unattractive for swimming due to the visibility of soap films in gray- water discharges. An additional concern is that illegal sewage discharges from private craft may occur and be visually difficult to distinguish from gray water. In the absence of a program of regular monitoring and inspection of boats on the lake to ensure compliance with regulations, the possibility remains that some " gray- water" discharges from private boats may contain sewage and result in unsanitary conditions. The potential for adverse environmental effects from gray- water discharges by watercraft has been inadequately investigated but appears relatively low. Soaps may contain phosphorus and other plant nutrients that encourage algal growth. In highly productive lakes the addition of nutrients sometimes results in overproduction of algae, with associated effects on the lake environment; at Lake Powell, however, nutrients are in such low supply that algae overproduction would not be expected from the limited quantities of soap materials involved. If unexpectedly large quantities of cleaners or other potentially toxic materials are being used on houseboats and discharged through sinks, then unforseen impacts could occur. The State of Utah has expressed some concern about whether gray water should be a prohibited discharge under their water pollution control regulations. This issue may hinge on a policy determination of whether gray water is a waste or pollutant that degrades water quality, since it is not explicitly mentioned as a prohibited discharge in the current version of the state regulations. At present, NPS is unaware of any regulation defining soap residues and small amounts of food waste as pollutants in this situation. In summary, gray- water discharge presents several management issues of unknown significance: the aesthetic effect on recreationists; the possibility of illegal sewage discharges being disguised by gray water; the effect of potential nutrient additions to the lake; and the possibility that gray water may be regulated by the State. 33 |
