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Mr.Steven Meeks - <br /> Environmental <br /> 28 August 2006 Resources <br /> Page 3 Management <br /> available thickness for product recovery is small, thereby limiting the <br /> recovery of the well. Multi-phase pumping and dual pumping systems <br /> combine ground water extraction to produce a cone of depression to <br /> maintain the accessible free-phase product saturated formation. <br /> However, since the site currently has a minimal amount of free-phase <br /> product, the cone of depression will cause a larger smear zone. The free- <br /> phase product will become entrained in the soils within this smear zone <br /> and will not be recovered by the skimmers. Therefore, UPRR proposes <br /> low vacuum SVE in conjunction with skimming at the site. Low vacuum <br /> SVE will still enhance the LNAPL content surrounding the extraction <br /> well while reducing the potential ground water upwelling or"smearing <br /> conditions." Figure 4 provides a schematic of a vacuum-enhanced <br /> product skimming. <br /> PROPOSED CONCEPTUAL DESIGN <br /> To increase the overall recovery of free-phase product from the site, <br /> UPRR proposes to install a vacuum-enhanced skimming system within <br /> MW-06A, PZ-01, and TW-01. Table 2 provides the well details for these <br /> three wells. Field activities will include the installation and connection of <br /> vacuum piping to these wells and installation of downwell skimmers. <br /> Since the existing DPE system has extraction wells relatively close to the <br /> proposed monitoring wells, UPRR proposes to trench between these new <br /> extraction wells and the existing DPE wells (DPEX-02 and DPEX-03) and <br /> then use the existing piping. The extracted product will be periodically <br /> removed and contained within a holding tank within the containment <br /> berm of the existing treatment system. If required by the San Joaquin <br /> Valley Unified Air Pollution Control District, the extracted vapors will be <br /> treated with either a granular activated carbon unit or a catalytic <br /> oxidation unit prior to discharge. <br /> CLOSING <br /> UPRR proposes to enhance free-phase product removal at the site with <br /> low vacuum SVE and free-phase product skimming. UPRR requests that <br /> the RWQCB review this proposal and provide formal concurrence with <br /> conceptual design. Upon receipt of this approval, UPRR will provide <br /> additional design details such as flow rates, vapor treatment options if <br /> required, and schedule. <br />