New Search
Water Resources <br />., <br />Ground Water Quality <br />Aquifers in the project area are recharged primarily by precipitation. The younger and older <br />alluvial deposits contain the most productive aquifers in the Willamette Valley; however, it has <br />been reported that these deposits are thin in the downtown area and have little potential for <br />ground water development. Geologically, the aquifers in the downtown area occur within the <br />Eugene Formation. This formation yields a limited supply of water to most wells, and the <br />ground water in deeper producing zones is considered too,saline for most uses (USGS 1973). <br />The city of Eugene's municipal water supply, provided by the Eugene Water and Electric Board, <br />is drawn entirely from the McKenzie River system, located approximately one mile north of <br />Eugene. The Springfield Utility Board, which supplies domestic water to the greater Springfield <br />area, has water rights drawn from several water wells within the city of Springfield, which it uses <br />to supply potable water to over 16,000 customers. No water is pumped from the Willamette <br />River for industrial or municipal supplies. For additional information on groundwater <br />characteristics in the project areas, consult the phase I environmental site assessments conducted <br />for this project (Herrera 2000a,b). <br />Significant Adverse Impacts <br />Short-Term Construction Impacts <br />Because the potential impacts of construction activities are similar for both of the alternative <br />sites, the following discussion of short-term impacts is equally applicable to all development <br />options under Alternatives 1 and 2. <br />Construction of the courthouse facility could result in short-term impacts from erosion associated <br />with excavation activities, and spills or leaks of toxic construction products and equipment <br />fluids. Soil erosion is typically the greatest concern for pollution related to active construction <br />sites, because it can result in offsite deposition of sediments, as well as impacts associated with <br />the transport of contaminants attached to sediment particles. Extensive soil erosion is not <br />expected for either of these alternatives, because much of the site construction disturbance would <br />occur below existing ground levels, and therefore limited surface runoff would leave the site. <br />However, ofsite soils adhering to the tires and undercarriages of construction vehicles could be <br />transported offsite and deposited on adjacent streets, then carried into nearby storm drains during <br />rain events. Likewise, soil hauled offsite could be inadvertently spilled onto nearby streets and <br />could enter the storm drain system. <br />The most common water quality impact associated with eroded soil and sediments on <br />construction sites is elevated turbidity in downstream waters, which reduces water clarity and <br />adversely affects fish and other aquatic organisms. Current state regulations allow for no more <br />than a 10 percent cumulative increase in natural stream turbidity. However, because of the large <br />size of the Willamette River relative to stormwater runoff volumes that would occur in the <br />project area, turbid construction site runoff would have minimal impact on the turbidity of the <br />river. <br />Final EIS 48 New Federal Courthouse <br />