10179096_2103 S. GRAND - Plan (2)

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Former Circuit One 2103 S. Grand Avenue, Santa Ana, California Proiect No. 11-0106 were analyzed for metals. The results of some metals total threshold limit concentration (TTLC) and/or soluble threshold limit concentration (STLC) testing conducted at that time are shown on Table 1 In July 1990, one composite concrete sample was analyzed for STLC. It appears that the concrete sample was from the five sampling locations shown in the southern part of unit 2105 S. Grand Avenue (Figure 3). The results of these samples are shown on Table 1. In October 1990, four soil samples collected from the sump and trench within the Site were analyzed for TTLC and/or STLC (GRI 1992). Sample B-1 was collected from the sump pit. Samples Comp-1, Comp-2 and Comp-3 were taken from the trench. The results of these samples are also shown in Table 1. Six of the wells were initially designated as B-1 through B-6 (GRI 1993). These wells were later designated MW-1, MW-3, P-2, P-5, MW-5 and MW-2, respectively. The locations of the wells are shown in Figure 4. As shown on Table 2, copper was not found in the groundwater samples that were collected in 1993. In November 2011, RS sampled 17 soil borings (SB-1 through SB-17) and soil samples from this borings were tested for VOCs and metals (RS 2012A). The location of the soil borings are shown on Figures 5 through 8. Soil samples from 2 and 5 feet each of this borings were tested for metals. Table 3 shows the results of the Title 22 metals testing. None of the metal concentrations exceed their TTLCs. Only two soil samples had copper that exceeded ten (10) times the STLCs for copper. The samples were SB-1-2' (1,000 milligrams per kilogram [mg/kg]) and SB-2-2' (1,400 mg/kg). Borings SB-1 and SB-2 are located near the former clarifier. The samples were analyzed for STLC and the results were 32 milligram per liter (mg/L) and 54 mg/L, respectively. In May 2012, twelve (12) five-foot soil borings (HA-1 to HA-12) were advanced by RS in suite 2103 to obtain soil samples for copper analyses (RS 2012B). The location of the soil borings are shown on Figures 5 through 8. Soil samples were collected at 1-foot intervals starting at 1- foot bgs to 5 feet bgs. The samples were analyzed for copper. None of the copper in the soil samples exceeded its TTLC of 2,500 mg/kg. However, some of the samples had STLC results greater than its STLC of 25 mg/L. At 1-foot, the area around borings HA-11 and HA-12 had copper above its STLC. At 2 feet, the soil around boring SB-1, SB-2, HA-11 and HA-12 has copper above its STLC. None of the soil samples collected at 3 and 5 feet contained copper at or greater than 10 times its STLC. Based upon the copper data obtained from the soil samples collected in suites 2101, 2103, 2105 S. Grand Avenue and the outdoor borings just south and north of the suites, it appears that the background copper concentration in this area is in the range of 19 mg/kg and 43 mg/kg. The copper in the 3 and 5-foot samples collected from borings SB-1 and HA-4 near the former clarifier are 130 and 150 mg/kg, respectively. This indicated that the copper released from the former clarifier had migrated at least to a depth of 5 feet bgs. RS in its report titled "May and June 2012 Site Assessment Report" that is dated September 4, 2012 indicated that groundwater samples collected by GRI in 1993 did not show that the groundwater in the area contained copper above its reporting limit and that copper released from the clarifier area did not appear to have entered the groundwater. In its letter dated September 19, 2012, the California Regional Water Quality Board - Santa Ana Region (CRWQB) indicated that the site conceptual model discussed in the RS report titled REMEDIATION SCIENCES 4