SITE INFORMATION AND CORRESPONDENCE

Home Browse Search

t 05/02/94 Groundwater monitoring wells MW-3 through MW-8 and MW-10 were abandoned beginning this date, by Ninyo & Moore. In addition, wells MW-9, MW-11, MW-13, MW-14, MW-16, MW-19, MW-20 and MW-24 were decommissioned by lowering the top of the well casing to allow for onsite construction. 09/30/94 Over-excavation of soil near SB-17 was performed starting this date. 09/07/95 Installation of soil vapor extraction well VW-1. Also, restoration of the wells decommissioned in May 1994. See Geocon's Problem Assessment Report and Corrective Action Plan dated December 9, 1996. 08/06/96 Well MW-11 over-drilled and new well reinstalled in same borehole; MW-25 and MW-26; VM-2 and VM-1 installed beginning this date. See Geocon's Problem Assessment Report and Corrective Action Plan dated December 9, 1996. 08/03/98 Wells MW-26 and VW-1 destroyed to make room for construction of a new shop. 02/08/99 Human Health Risk Assessment/Groundwater Impact Analysis was submitted by Woodward Clyde. 03/01/00 Depth discrete sampling with a Kabis sampler and a slug test were performed. See Additional Groundwater Study submitted this date by URS Greiner Woodward Clyde. 11/15/01 Beginning date of site investigation work; well MW-14 destroyed and reinstalled, CPT boring and sampling boring installed. See Geocon's Monitoring Well Destruction/Installation Report dated December 26, 2001. 06/03/05 Four air sparge points (ASW-1 through ASW-4) and two vapor extraction wells (VEW-1 & VEW-2) installed beginning this date. See Secor International Inc.'s Second Quart=er 2005 Operations Maintenance and Monitoring Report dated August 5, 2005. 12/01/05 Remediation of the site began with startup of the soil vapor extraction air sparging SVE/AS system. The system operated until June 25, 2009. Three rebound events were conducted prior to shut down. The system removed approximately 28,150 pounds of hydrocarbons during its operation. 10/08/09 Two confirmation soil borings were advanced and three shallow temporary soil vapor wells were installed onsite. See Stantec's Closure Report Caltrans Stockton Shop 10 dated December 2, 2009. 12/02/09 Closure Report Caltrans Stockton Shop 10 submitted this date by Stantec. In the Report Stantec recommends site closure. Soil and groundwater contamination has been remediated to the point practicable; remaining soil contamination is longer chain diesel, groundwater concentrations are declining, soil vapor results indicate no unacceptable heath risks, and concentrations of 1,2-DCA will reach the MCL within 4.5 years.