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Ms. Ann Kolata SBI070.400.0002 October 15, 2013 Page 3 sampling depths using a non - phosphatic detergent (e.g., Liquinox) and rinsing with distilled water. Soil samples will be selected based on Hull's field observations. In general, those samples exhibiting the highest PID readings or other evidence of impact will be selected for chemical analysis. In addition, a second (deeper) soil sample may be selected and submitted to the laboratory to evaluate the vertical extent of contamination. If samples in a given boring exhibit little variation in the degree of apparent contamination, Hull's field representative may preferentially select the surface sample (i.e. 0 to 2 ft. bgs) for analysis. Unused samples will be placed in a Department of Transportation- approved 55- gallon drum. The driller will decommission the borings by filling the boreholes with bentonite chips. Note that because Hull's drilling subcontractor will likely issue a single invoice for the soil borings and the temporary groundwater sampling points, subcontractor costs for the soil boring installation are included in Task 3 for purposes of this cost estimate. Task 3 Install Temporary and Permanent GW Sampling Points Additional on -Site groundwater sampling to evaluate the potential impact from COCs associated with the former Oliver foundry is required. As presented in the December 2011 RWP, a limited number of groundwater samples within the footprint of the former foundry have been proposed, and IDEM agrees with this approach. Also, as we have discussed, an evaluation of the extent to which off -Site sources may have impacted groundwater underlying the Site is necessary. The installation and sampling of a series of temporary groundwater monitoring points within City right -of -way along Arnold Street south and west of the Site (i.e., across the upgradient section of groundwater entering the Site's southwest parcel) will aid in evaluating where off -Site sources may be contributing to the groundwater impacts that have been observed at the Site. Based on the results of the temporary sampling completed in this Task, additional permanent groundwater monitoring wells may be needed within City right -of -way along Arnold Street, as described below. Also, as requested by IDEM, and as proposed in Hull's August 1, 2013 letter, four monitoring wells are necessary north (i.e., downgrodient) of the Site at locations that will be acceptable to the City, property owners of the Kroc Center, and property owners of the Laurel Place Apartments. Following the installation of these newer monitoring wells, the top of casing and ground elevations of the new wells, as well as the elevations of PMW- 11, MW -135, and MW -14S [which were cut down during construction of the Underground Pipe & Valve (UP &V) facility], will be surveyed so that the groundwater elevations measured in these wells can be compared relative to the other wells in the monitoring network. Hull will install the initial temporary groundwater sampling points within the right -of -way of Arnold Street, between Poland Street and West Sample Street, as discussed below. Please note these sampling locations have been selected to evaluate the potential presence of an upgradient source of the impacts detected in MW -1, which is the most upgradient groundwater sampling point at the Site, and is also where the highest groundwater impacts at the Site have been historically detected. Hull will also install temporary groundwater sampling points within the footprint of the former Oliver foundry during the some mobilization. In general, our proposed approach entails defining the vertical extent of chlorinated volatile organic compounds (VOCs) upgradient of MW -1 by installing four relatively shallow and four relatively deeper temporary sampling points (installed at four nested sampling locations) within the right -of -way of Arnold Street; installing permanent monitoring wells north of the Site while laboratory analyses on the samples from the temporary points are completed; and installing three permanent sets of nested monitoring wells upgradient of MW -1 (again, within the right -of -way of Arnold Street) at appropriate locations once the vertical extent is