ADDITIONAL BACKGROUND INFORMATION Mercury Mine Remediation Program To produce quicksilver, mined ore was heated in "retorts" (furnaces that vaporized the mercury) and then condensed. During this refining process, mercury was spilled on the ground and lost to the atmosphere. The waste rock and tailings (processed ore) were simply dumped downhill— often directly into streams—where they conveniently eroded away in winter storms. These contaminated materials were deposited downstream, and now slowly leach and erode back into local creeks. Abandoned mine sites in the upper watersheds and their legacy contamination downstream are a significant contributor to water quality impairments in our region. Mercury is a powerful neurotoxin when converted to methyl mercury (MeHg). Inorganic mercury is converted to MeHg by certain bacteria prevalent in creek sediments, lakes and wetlands. The concentration of MeHg in the water column is controlled in part by the concentration of total mercury in the sediment and the rate at which the total mercury is converted to MeHg. MeHg “bioconcentrates” up food chains, magnifying fish levels up to 10 million times more concentrated than in water. Eating contaminated fish can result in neurological damage particularly in pregnant women and children. This can be particularly dangerous to subsistence fishing families who rely on fish for both cultural and economic reasons. There are about 100 abandoned mercury mines in the Cache Creek and Putah Creek watersheds. Some of the more well-known sites include Knoxville, Oat Hill, Aetna, and Helen mines in the Putah Creek watershed and the Sulphur Bank, Abbot-Turkey Run, Wide Awake, Elgin and Petray-Rathburn mines in the Cache Creek watershed. The Westside Sacramento Integrated Regional Water Management group (http://westsideirwm.com/) is implementing a project in 2016-2018 to assess the mine site legacy in these watersheds. Mercury ore is often formed along fault lines associated with serpentine rocks. Serpentine was originally part of the ocean crust that was hydrolyzed and thrust to the surface in the plate tectonic process. Hot liquids carrying mercury, gold and other metals traveled along the fault lines between the serpentine and other rocks to form ore bodies. Cedar Roughs, Knoxville and Walker Ridge have large serpentine rock areas.