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Taj Bahadori <br /> Page 3 of 9 <br /> December 23,2014 <br /> central and northern Sierra Nevada Mountains were completely covered with a thick blanket <br /> of andesitic volcanic rocks known as the Mehrten Formation. <br /> The Mehrten was continuously deposited over an extended period of time, as long as 10 <br /> million years. These rocks include andesite conglomerates, welded tuffs, lava flows, and <br /> lahars. The Mehrten Formation therefore consists of a series of conglomerates, tuffaceous <br /> sandstones, siltstones, and claystones derived from this andesitic source material. <br /> Permeability is generally low. The Mehrten Formation soils are reworked volcanic mudflow <br /> deposits that contain stream deposited silt, sand,and minor gravel. <br /> The Mehrten was laid down by chaotic volcanic activity over an expanse of time of many <br /> millions of years from many volcanos that would have gone through periods of dormancy that <br /> could have lasted as long as several hundreds to several thousands of years. This genesis of <br /> deposition would not likely produce a uniform sequence of material. The claystones and <br /> sandstones derived from these volcanic eruptions may not be laterally continuous throughout a <br /> region. However, the water bearing zone beneath the Foothill Landfill appears to be one <br /> continuous sandstone unit. <br /> Geologic Map of the Foothill Landfill Area <br /> Basalt <br /> - Tehama <br /> � Formation <br /> Laguna <br /> Formation <br /> San Pablo <br /> Group <br /> 4. Mehrten <br /> z <br /> � Formation <br /> Valley Springs <br /> Formation <br /> Maddey <br /> Sandstone <br /> n "* * 06th1 I 8f1 tdty Nortonville Shale <br /> ' landfill <br /> Domenglne <br /> Yn S. <br /> 4' Sandstone <br /> Capay Fonna6on <br /> Y r, <br /> IE <br /> a <br /> �. "Aur{teroue <br /> " xa* Gravels <br /> MW-6 Design.docx <br />