To that end, there are numerous publications within the Basin aimed at property owners and visitors to sensitize those that enjoy the Basin as to the potential sources of contamination and means for control. The physical and institutional characteristics of the Tahoe Basin, including existing regulatory controls, size, depth, residence time within Lake Tahoe, and watershed activities appear to provide a physical barrier preventing the introduction of microbial contaminants into the raw water supply for those purveyors with appropriately designed intakes. In this instance, water quality in Tahoe appears at least as high as that from a controlled watershed. Based on the monitoring results for microbial constituents, Giardia and Cryptosporidium concentrations are in the range found in controlled watersheds. Watershed controls, such as those imposed by the TRPA Code of Ordinances, U.S. Forest Service practices, and other agencies with jurisdiction in the Basin, appear adequate to minimize the introduction of microbial contaminants and excessive turbidity to the water supply.
Source control is the first barrier in a multiple-barrier treatment train.
Public confidence in the water supply will be shaken if the source water quality is known to be contaminated. The participating water utilities should continue implementation of BMPs associated with the sanitary survey results, including a comprehensive public education program, surveillance of the watershed, optimization of the operation and maintenance of all water and wastewater facilities, and continuation of the capital program to reduce sediment transport and improve storm water runoff to the lake. The efficacy of BMPs in reducing potential contamination should be evaluated to assure cost-effective use of public funds. All utilities participating in the filtration avoidance program in Lake Tahoe have demonstrated that their facilities exceed the requirements for filtration avoidance, and should continue monitoring for microbial contaminants. As some pathogens are difficult to analyze for, remove, and disinfect with conventional treatment methods, keeping them out of source water may be the only way of providing multiple-barrier treatment.