WORK PLANS - Laserfiche WebLink

Home Browse Search

Revised Workplan-Additional Site Investigation for PFAS BSK Project E20-016-01F Stockton Metropolitan Airport(SCK) March 1, 2023 Stockton, California Page 10 4 PURPOSE OF THE INVESTIGATION The intended purpose of this additional site investigation at SCK is as follows: • Install groundwater monitoring wells to better understand local gradient in the subsurface under the SCK property. Additionally, the monitoring wells will serve as data points to aid in characterization of groundwater below SCK property. • Delineate the lateral and vertical extents of PFAS compounds in soil and groundwater in the subsurface in PRA 1 and PRA 2. Please note that depending on findings, additional phases of investigation may be necessary to accomplish this goal. • Summarize information regarding the storm drain network provided by the airport, including stormwater flow direction, and any stormwater retention and/or treatment system available to SCK, and ultimately evaluate if PFAS is being transported off SCK property. • Prepare a report of findings, documenting BSK's investigation and any conclusions or further recommendations. The following describes a project approach based on BSK's understanding of project requirements at SCK. 5 PROJECT APPROACH To further assess the nature and extent of PFAS in soil and groundwater at SCK, it will be necessary to complete the work in two (2) separate mobilizations. Therefore, the following project approach will be divided into "First Phase" and "Second Phase". The following project approach will be employed for the First Phase of investigation at SCK: 1. Mark the site for Underground Service Alert (USA) North to assess and mark utilities in and near PRA 1, PRA 2 and PRA 3. Additionally, BSK may contract a private utility locator to assess PRA 1, PRA 2 and PRA 3 regarding utilities below the ground surface which may be owned by the airport, or not included on airport plans. Furthermore, due to airport activities, some utilities may be buried deeper than typical utility depth. 2. Once boring locations have been cleared, BSK's licensed drilling subcontractor will advance six(6) Direct Push Technology(DPT) borings in PRA 1 and eight (8) DPT borings in PRA 2 using the step out method to a depth ranging from 10 ft bgs to 40 ft bgs. Soil samples will be collected for chemical analysis from depths of 1, 5 and 10 ft bgs. DPT borings advanced beyond 10 ft bgs, will have additional soil samples collected for chemical analysis every 5 ft after the 10 ft sample (i.e., 15 ft, 20 ft, etc.,).These borings will be used to evaluate the vertical and lateral extent of PFAS in soil.