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.-B~. three lakes area are the Grand Lake wastewater treatment facility, the Shadow Mountain Govern- ment Camp wastewater treatment facility and the numerous individual subsurface disposal systems serving homes and businesses along the shores. Effluents from the two treatment facilities are the largest point sources of nutrients entering the lakes. Analyses of the Grand Lake wastewater treatment facility effluent, the largest wastewater discharge, showed average inorganic nitrogen, orthophos- phate and total soluble phosphorus concentra- tions l3.43 mgN/l. 5.21 mgP/l, and 6.l4 mgp/I respectively. In terms of total load, this plant provided only 0.28 percent of the total inflow to the lakes but supplies 36.0 percent of the inorganic nitrogen, 68 percent of the or tho- phospa~e and 21.5 percent of total soluble phosphorus loads to the lakes during this survey. Therefore, advanced waste treatment methods including at least 80 percent ortho- phosphate removal, wastewater export, or total containment of effluents in ponds will be re- quired to preserve the present water quality and reduce the nutrient concentrations in the lakes. I 4. The concentration of orthophosphate, the phosphorus form most readily available for biological growth, is sufficiently high that anyone or all three of the lakes could sustain nuisance algae blooms. Wastewaters contributed the major portion of orthophosphate to the lakes with the Grand Lake wastewater treatment facility alone contributing 68 percent of the measured orthophosphate load. It is estimated, based upon data obtained in this survey, that the combined wastewater flows contribute more than 80 percent of the annual orthophosphate load. The low inorganic nitrogen concentrations I existing in the lakes and inflows and the presence of Aphanizomenon flos-aquae and Ana- baena sp., both atmospheric nitrogen fixers, indicate that the lake waters are nitrogen deficient and the phytoplankton growth is nitrogen limited.