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Stockton Promenade—N. Edisonp'treet USTs& Utility Corridors Page 7 Underground Storage Tank Removal Report - June 8,2009 WKA No,7345.09 A water sample, representative of the contents draining from Tank#1, was collected from the excavation floor immediately after the tank was removed. The water sample was collected in 90- milliliter VOA vials. This water was not considered to represent shallow groundwater conditions ' as the former Tank#1 excavation area was later dug to approximately 10 feet bgs and did not encounter shallow groundwater. All samples were sealed, labeled, and placed in a chilled thermally insulated container for transport to the analytical laboratory (see discussion of results in Section 5.0). 2.6 Backfilling ' On December 5, 2008 and January 15, 2009, representatives from WKA observed the placement of backfill materials back within the former UST excavations. A demarcation liner was installed ' in each excavated area prior to backfill activities and the excavated soil from each respective tank area was placed back into the hole for later removal. Because this area was slated for later excavated for underground utility corridors and road construction, backfill into the former UST excavations was not compacted. 3.0 EXPLORATORY TEST PITS ' After removing the four USTs, WKA monitored the digging of six exploratory test pit ' excavations in the area between the WOTOA parking lot and the removed USTs to identify whether additional USTs, unidentified piping, or petroleum hydrocarbon impacted soil may be present and would require mitigation prior to installation of the proposed underground utilities. On January 15, 2009, WKA monitored the excavation and collected samples from 5 exploratory test pits (EP-I through EP-5) at locations surrounding the former USTs (Figure 3). A sixth ' location, EP-6, was excavated to identify whether a UST was located at that position. Soil samples were not collected at the EP-6 location because no UST was discovered. The exploratory test pits were excavated to depths ranging from 6 to 18 feet bgs and varied in length, depending on the observed soil conditions and debris encountered at each location. Excavation activities were conducted using a backhoe under the oversight of a WKA field geologist. All sample depths ' were measured with respect to the existing ground surface of the mounded area at the time of field activities.