The Real Story Behind 'Mercury Impaired' Reservoirs and Lakes

A recent news article (LA Times, July 29, 2016) stated that the State Water Resources Control Board has declared numerous California reservoirs and lakes as "mercury impaired" because they have sampled fish from those reservoirs with methylmercury levels exceeding 0.2 milligrams per kilogram of fish tissue (or 2 parts of mercury per ten million parts of fish tissue). Lake Sherwood had the highest level detected at 0.65 mg/kg. Already the SWRCB has placed 85 lakes and reservoirs on their 303(d) list (Federal Clean Water Act reference) as impaired for mercury. Some familiar names appear in the list: Arrowhead, Big Bear, Casitas, Castaic, Folsom, Nacimiento, Oroville, Pyramid, San Antonio and San Luis. Some lakes with a reputation for pristine water quality are also in the list, such as, Hetch Hetchy, Shasta and Trinity.

Thus far, neither the Tehachapi-Cummings County Water District (owner of Brite Lake) nor the Tehachapi Valley Recreation and Park District (recreation manager of Brite Lake) have been notified of any mercury contamination in Brite Lake. However, Brite Lake does appear in the SWRCB's latest list of lakes and reservoirs along with 82 others that are shown as possibly being listed in the future. Although we have been made aware of the possible future listing, the SWRCB has not provided any data in regards to mercury contamination nor even notified us that any fish were sampled.

As to their maximum contaminant level of 0.2 mg, some additional information would be helpful. Several types of fish readily available in supermarkets have average mercury concentrations higher than 0.2 mg, such as, halibut (0.24) albacore tuna (0.35), orange roughy (0.57), king mackerel (0.73), shark (0.98) and swordfish (0.99). Many other species of fish have low mercury concentrations.

source: http://www.fda.gov/Food/FoodborneIllnessContaminants/Metals/ucm115644.htm.

Some types of fish caught in foreign waters have mercury concentrations higher yet. Consequently, the Food and Drug Administration has issued guidelines as to how much fish people should eat and which types of fish are lower risk, with particular guidelines for children and pregnant women.

See http://www.fda.gov/food/foodborneillnesscontaminants/metals/ucm393070.htm.

There is much more information available from the FDA about the health risks of eating fish. If you have a particular concern, you should ask your health care professional.

So, the Water District has not taken any actions regarding fish in Brite Lake because we have not been notified that there is any problem. There has been some speculation in social media that perhaps the mercury issue had something to do with the low water level in Brite Lake. The two issues are unrelated. Brite Lake is low right now because of three factors: 1) agricultural activity has increased with hundreds of additional acres being added in 2016; 2) we suffered through a recent heatwave, which has extended the peak irrigation demand season; and 3) the Water District's importation system was not fully functional in April and May because of the engine replacement project that was done during the off season. The four natural gas engines at Pump Plant 1 no longer complied with the Valley Air Board's pollution regulations, so they were replaced with new state-ofthe-art engines. Integrating those engines along with the new engine controls and the system-wide automation proved challenging with the result that the Water District was "behind the curve" importing water in April and May. We have been at full flow for the past two months. Next year, with the new engines in place, Brite Lake should be in excellent shape for the summer season.