Accelerated Operable Unit 1 (AOU. 1) AOU-1 contains the ESS located within the East Bench area of Salt Lake City. The springs and seeps are an expression of groundwater that surfaces along the Wasatch Fault (Figure 2). The investigation and remedial approach to AOU-1 has focused on defining and mitigating vapor intrusion arising from shallow groundwater contamination in this area to ensure that public health risks are minimized while the long-term planning and investigation process for the site are ongoing. AOU - 1 is within Sections 4, 5, 8, and 9, Township 1 South, Range 1 East, of the Salt Lake Base Meridian. The area is located in the residential Xxxx Xxxxxxx, Xxxx Xxxxxxx Xxxx, Xxxxxxxxx and Gilmer Park neighborhoods on the Xxxx Xxxxx xx Xxxx Xxxx Xxxx, XX (see Fig. 3). AOU - 1 boundary is tentatively defined between 800 South and Michigan Avenue and 1100 East and 1300 East. The general topography slopes to the west with an average elevation of 4,520 feet above mean sea level (USGS, 1975). A portion of the Wasatch Fault is located in AOU - 1; it is a normal fault because the displacement is mostly vertical with the mountain block (Wasatch Range) moving upward relative to the adjacent downward-moving valley block (UOS, 1996). Red Butte Creek is located to the south of AOU-1 and runs to the west towards Liberty Park Pond. The goal of AOU - 1 remedial investigation (RI) is to identify the potential for, and if necessary, mitigate vapor intrusion, early in the Site’s remedial investigation process using removal action authority to address individual locations, if necessary The AOU - 1 Remedial Investigation Work Plan (RIWP) focuses on indoor air; groundwater and surface water characterization within and adjacent to the ESS and providing data for assessment of the human health risk posed by exposure to the contaminated groundwater and vapors that originate from the contaminated groundwater. An environmental risk screening is also done at any habitat location sampled during the RI. The RIWP includes all required plans (Health and Safety Plan, Sampling Analysis Plan, Quality Assurance Project Plan, Risk Assessment Work Plan, etc.) needed to support evaluation of the potential for vapor intrusion in residences, businesses, and schools. AOU - 1 field work commenced in late Fall 2014/Early Winter 2015 with interviews of property owners who volunteered during the March and September 2014 public meetings. The initial phase of indoor air and soil gas sampling commenced in early January 2015 and wa...
