REGIONAL GEOLOGY AND HYDROGEOLOGY. The Site is located in the City of Medford, which lies within the upper Rogue Valley, on the edge of the Siskiyou Mountains, which are part of the Klamath Mountain Range that extends to the Pacific Ocean and divides southern Oregon from northern California. The Klamath Mountains are composed primarily of volcanic and sedimentary materials that have been folded and faulted and contain intrusive and metamorphic rock. (12) Medford is situated on stream deposits and sedimentary rock deposited about 50 million years ago. The Rogue Valley is bounded by the Siskiyou Mountain Range to the south, the Cascade Mountains to the east and the Coast Range to the west. The interior valley framed by these ranges contains the urban areas of Medford and several surrounding communities (13). They are built on flood plains, stream terraces, and flat to gentle slopes. The Site has an elevation of approximately 1420 feet above mean sea level. Bear Creek, one of the Rogue River‟s primary tributaries, flows directly through the City of Medford from south to north. Bear Creek is the major discharge for floodwaters. The Bear Creek Watershed is comprised of 83 streams in 21 sub-watersheds. These waters drain into the Rogue River west of the White City industrial area. Bear Creek has been one of the major salmon spawning tributaries to the Rogue River. In addition to these natural waterways, a complex irrigation canal system surrounds the City to the east and west, transporting irrigation water in the summer and stormwater during storm events (13, 14). Medford has a moderate, seasonal climate. The average daily high temperature in the city is between 80 and 95 degrees in the summer and between 25 and 45 degrees in the winter. The Rogue Valley has the lowest precipitation among Oregon‟s western interior valleys, with Medford averaging about 19 inches of rain per year. This average includes a wide range of rainfall values over the past 18 years that have been as low as 10.69 inches in 1985 and as high as 31.41 inches in 1996. Rainfall occurs primarily in the winter months (13, 14).
REGIONAL GEOLOGY AND HYDROGEOLOGY. The Keizer area is situated predominantly on the present-day floodplain of the Willamette River, which in this area is known as Keizer Bottom (the southern end of Mission Bottom). Keizer Bottom slopes gradually downward towards the north into the main area of Mission Bottom. The whole of Mission Bottom covers an area of about 23 square miles extending from North Salem northward towards Mission Bottom State Park, and is bounded by the Willamette River on the west and French Prairie on the east and south (Price, 1967). French Prairie is an older river terrace (formed in the Pliocene and reworked by flood deposits in the Pleistocene) approximately 30 to 80 feet higher in elevation than Mission Bottom, which is well-defined on the USGS topographic map (see Figure 1, site location map). Xxxxxxxx Creek, an ephemeral stream, drains the eastern and southern portion of the Keizer area northward towards the Willamette River and defines the boundary between Keizer/Mission Bottom and French Prairie. On the western edge of the study area, the floodplain terrace drops 10 to 20 feet to the Willamette River. The Willamette Valley is a structural depression with hills of moderate relief separating broad alluvial flats. It lies between the Cascade Range and the Coast Range and extends from the Portland Basin southward to a point near the city of Cottage Grove. The Willamette Valley consists of numerous terraces and reworked floodplains mostly of Pleistocene and recent age (Price, 1967). Regional geology consists of a stratigraphic sequence of largely Quaternary sediments and flow deposits associated with the Willamette River and its tributaries, overlying older parent rock including Cascade volcanic and Columbia River Basalts. In the Willamette Valley, surficial basin deposits include alluvium and flood deposits that are often grouped together and are commonly referred to as the “over-bank deposits.” First-occurring groundwater is typically encountered in the “over-bank” units as the unconfined water table aquifer. Published area-wide groundwater studies conducted during the 1960s indicate that the alluvial aquifer in the area generally flows to the northwest, where it discharges to the Willamette River. Keizer Bottom geology consists of over-bank deposits containing approximately 15 to 20 feet of silt/clayey silt overlying sand and gravels and some cemented gravels (Troutdale Formation) to a depth of greater than 100 feet. Columbia River basalts underlie the Troutdale Form...
REGIONAL GEOLOGY AND HYDROGEOLOGY. The geology and hydrogeology are important factors for the migration and mobilization of coal ash pollutants in the environment. Juliette, GA and Plant Xxxxxxx are located in the Piedmont Physiographic Province (PPP) of Georgia, used to describe the area’s land formations, elevation, rocks and minerals, and soil characteristics. The PPP is the second largest province in the state and has the highest population. It lies between the mountains of north Georgia and the Fall Line [23]. Metamorphic and igneous rocks make up the underlying bedrock and weathered layers of the PPP. These rocks have been exposed to physical and chemical weathering, resulting in a landscape marked by creeks and streams that form a dendritic drainage pattern. Bedrock in this region is typically overlain with residual soils and saprolite. The depth of weathering in the PPP is generally 20 – 60 feet, but may extend to depths greater than 100 feet in some areas. The depth of weathering in the PPP can vary significantly due to variations in rock type and structure [22]. Residual soils are formed when rocks weather due to chemicals, water, and other environmental elements and remain in the same location. Residual soils in the PPP largely consist of xxxxx silt, silty sand, xxxxx xxxx, and silty clay, and lie at variable thickness atop the bedrock. Thickness of residual soils in the region determined by boring showed a range of approximately 17 – 168 feet [22].
