SU0008578 - Laserfiche WebLink

Home Browse Search

5.ENVIRONMENTAL CHECKLIST MOUNTAIN HOUSE NEIGHBORHOODS K AND L INITIAL STUDY 7.HAZARDS connection with the Neighborhoods K and L sites.The Phase I ESA investigated previous ownership and uses of the sites to partially satisfy the innocent landowner defense' to the Comprehensive Environmental Response, Compensation and Liability Act(CERCLA)and to document those environmental. conditions that could potentially affect development. A Limited Phase II ESA was also prepared to evaluate recognized environmental conditions for Neighborhoods K and L identified in the Phase I ESA(Condor,2004b). The Phase II ESA more closely evaluates potential contamination issues and potential health risks associated with historical agricultural land use practices at the sites. Site Topography and Natural Features Mountain House is located in the upper San Joaquin River Valley of the Great Valley Geomorphic Province of California. The Great Valley is an alluvial plain that is drained by the San Joaquin and Sacramento Rivers through San Francisco Bay. Mountain House Creek, Dry Creek, and Old River are the primary drainages for storm water runoff at Neighborhoods K and L. Mountain House Creek originates in the Altamont Hills and flows southwest to northeast between Neighborhoods K and L to Old River at the northern project site boundary. Dry Creek runs parallel to Mountain House Creek and traverses the westernmost corner of Neighbor- hood K before discharging to Old River. Old River flows east to west along the northern project site boundary. The ground surface in and around Neighborhoods K and L is generally level and slopes gently(less than one percent) northeast toward Old River. The average ground surface elevations in Neighborhoods K and L are approximately 10 feet above mean sea level (msl) and 18 feet above msl, respectively, However, ground surface elevations range from 0 feet above msl along the northern site boundaries at Old River to 25 feet above msl in the south. Generally,groundwater flows as a subdued reflection of the surface topography. During subsurface investigations conducted in 2007 and 2010,groundwater was encountered in all soil borings in Neighborhood K at depths of 3 to 12 feet below the ground surface(bgs)and in Neighborhood L at 4.5 to 14.5 feet bgs(Engeo, 2007,2010). Past and Present Land Use Agricultural land uses have dominated Neighborhoods K and L since the early 1900s. The primary crop types cultivated at these sites included alfalfa, sugar beets, corn, and wheat(SJCCDD, 1994). Pesticides and herbicides have been used on the sites due to past and present agricultural land uses and represent 1 The"innocent landowner defense"is the defense to the CERCIA liability.One of the requirements of this defense is that the party make"all appropriate inquiry into the previous ownership and uses of the property consistent with good commercial or customary practice." I9nm1 5-84