No Project associated with this Finding

Why Measure for Toxins?

In an oligotrophic system like Lake Tahoe with no industrial effluent, toxic compounds are typically not an issue lake-wide. However, there are exceptions such as MTBE, BTEX PAH compounds associated with motorized watercraft (Rowe 2012), toxicity associated with urban stormwater (Lopus et al., 2000) and the identification of mercury in deep Lake Tahoe sediments and biota (Heyvaert et al., 2000). In addition, toxics may enter the Lake through localized spills or some other transient pathway(s). The later often requires rapid response monitoring and therefore would be outside the purview of the routine nearshore monitoring program developed herein. The agencies should refer to their own protocol for sampling under such conditions as well as the rapid response monitoring plan developed recently (Lake Tahoe Geographic Response Plan, 2007), along with some guidance available from the science community (Gertler et al., 2011). Measurement of toxics in the nearshore should follow federal guidelines and requirements established by the states of California and Nevada, and the TRPA, when appropriate. At this time it is expected that any sampling for toxic pollutants in water and sediment would be targeted in response to specific incidents or potentially new emerging concerns identified by the regional water quality management agencies.

Monitoring Data Summary

Monitoring for micro-organisms that may affect human health requires full coordination with the Lake Tahoe water quality regulatory agencies. In recent years, the agencies have monitored coliforms and E. coli at 23 nearshore/beach locations, including, Kings Beach, Lake Forest, Tahoe City Commons, McKinney-Chambers Landing, Sugar Pine Point-Shoreline, Sugar Pine Point-Boat Area, Meeks Bay, D.L. Bliss-Shoreline, D.L. Bliss- Boat Area, Emerald Bay Shoreline, Emerald Bay Boat Camp, Ski Beach, Baldwin Beach, Kiva Beach, Camp Richardson, El Dorado Beach near boat ramp, Timber Cove, Lakeside Beach, Nevada Beach, Zephyr Cove, Sand Harbor, and near the mid-lake-TRG buoy, with the latter included for reference. This monitoring was primarily done during the summer and early fall in coordination with public use of the beaches. Coliforms and fecal coliform concentrations also have been measured as part of the TRPA’s annual water quality Snapshot Day, a volunteer program that collects samples in May from various locations around Lake Tahoe and the Truckee Watershed. In addition, members of the Tahoe Water Suppliers Association report results from monthly sampling of intake water and in some cases from sampling at local beaches.

Recommended Monitoring

The nearshore science team believes that the agencies should continue this monitoring in accordance with the established state and federal requirements for the protection of drinking water and swimming and other water recreation. In particular, the synoptic beach monitoring should occur each year during peak recreational use periods, e.g. the July 4th and Labor Day holidays or weekends between. While E. coli is a widely accepted indicator of fecal contamination, new research on various harmful micro-organisms continues to evolve, and agencies should keep abreast of the latest U.S. EPA requirements for bacterial indicator organisms.