WORK PLANS FILE 1 - Laserfiche WebLink

Home Browse Search

�1 C�edogical Technics tnc. Page 2 Dual Phase Extraction Pilot Test Work Plan Valentine(Castle Motors) v Project No. 764.2 September 8,2003 • In August 1999, one deep screened monitoring well (MW-101) and one soil boring SB-201 were installed at the site. The purpose of these borings was to define the vertical extent of the groundwater plume. Soil samples collected by use of the SimulProbe" Maxitool from the soil borings tested positive for BTEX and TPH-G compounds to a depth of 111 feet. Pore water samples, also collected with the SimulProbe, revealed the presence of BTEX and TPH-G to a depth of I I I feet bgs. • An abandoned domestic well located at an adjacent residence was destroyed in accordance with SJC/EHD directives on April 20, 2001. • A discretely screened deep well (MW-201) was installed in October 2001. The results of this endeavor suggested that the contamination extended to a depth of 128 feet below grade surface (bgs). This depth was the target of a SimulProbe sampling effort and the soil sample from this elevation contained detectable TPH-G. 0 Seven quarterly monitoring events have been completed since the installation of deep well MW-201. This well was completed with a screened interval of 148 — 150.5 feet bgs. The amount of contamination in this well has attenuated to trace levels suggesting that it was a drilling artifact. • In a letter dated April 29, 2002, Mr. Jeff Wong of SJC PHS/EHD issued a letter directing that a work plan for the investigation of the lateral and vertical definition of the plume be submitted by July 1, 2002. GTI submitted an "Additional Site Characterization Work Plan" dated June 27, 2002 to SJC PHS/EHD. The work plan included provisions for installing one additional on site deep screened well, and three off site well clusters consisting of a shallow, intermediate and deep well at each location. In their October 22, 2002 correspondence, SJC PHS/EHD approved the GTI work plan with modifications: the deep screened well and the off site well clusters were disapproved. Instead, SJC PHS/EHD required that continuous multi- chambered tubing (CMTTM) wells be used instead of discretely screened, multiple PVC wells. In addition, SJC PHS/EHD also required that the first boring be continuously sampled to determine off site lithology. The work is awaiting encroachment pen-nits from the City of Stockton before proceeding. v GTI has developed the following plan to evaluate the feasibility for using dual phase extraction to clean up of the soil and groundwater plumes. This work can proceed concurrently with the continued plume definition efforts. 2.0 FEASIBILITY STUDY- DUAL PHASE EXTRACTION TEST V Soil vapor extraction and groundwater extraction are two proven technologies for the remediation of gasoline impacted sites. Dual phase extraction involves the use of both technologies simultaneously from one well - extracting groundwater induces a cone of depression that exposes more impacted soil to vapor extraction. For the purpose of this pilot test, GTI proposes to utilize a mobile treatment unit for a period of one week. Extracted vapors will be treated with a thermal oxidizer and groundwater will be treated and then pumped into the City of Stockton municipal sewer for disposal. Tables 1 & 2 in Appendix A contain the soil and groundwater analytical data generated for the site.