2009 Monitoring Results - Fecal Indicator Bacteria, PAH, BTEX

No Project associated with this Finding

Finding Details

For watercraft-associated gasoline pollutants (benzene, toluene, ethylbenzene, andxylenes or BTEX), a total of 20 locations were sampled on 5 occasions from June-October 2009, to during the peak boating and non-peak boating season. Samples sites included areas of possible changes in Shorezone development and represented areas of low, moderate and high boat traffic around Lake Tahoe. To measure longer term toxicity, semi-permeable membrane devices (SPMDs) were placed at 10 of the 20 locations for a 30 to 34 days period to provide a time-integrated concentration of polycyclic aromatic hydrocarbons (PAH) and to estimate the bioavailability to aquatic biota. Nineteen beach sites, 3 boat-only, and 1 mid-lake reference site were sampled to determine bacterial concentrations. Results from 2009 water quality indicated extremely low concentrations of gasoline constituents and PAH when compared to State and Federal standards and previous water quality data. For PAH, 32 PAH compounds were detected and/or estimated from SPMD devices; the concentration of these compounds, like BTEX were also extremely low. Bacterial contamination was documented at all of the beach sites; however contamination was not detected at boat-only sites or at the mid-lake reference site. Bacterial concentrations at some sites were greater than State standards, but concentration were never detected above levels that would require beach closures.

2009 Shorezone Monitoring Report