WORK PLANS - Laserfiche WebLink

Home Browse Search

Treatability Study Report and Feasibility Evaluation for In Situ Petroleum Hydrocarbon Remediation Field Maintenance Shop #24, 8020 South Airport Way Stockton, California 1.3. TREATABILITY STUDY TECHNOLOGY DESCRIPTION The following is a general description of the technology associated with the SVE, AS, and HVDPE treatability study. Specific details associated with implementing these technologies for the treatability study at the site are presented in Sections 2 through 5 below. The objective for evaluating these technologies is to determine the degree to which they might be effective in enhancing the removal of COPCs from soil and/or groundwater at the site, and in preventing further migration of COPCs in groundwater. Technical information obtained during implementation of these treatability studies is the basis for evaluating the technical feasibility of the technologies (or a combination of them) for future remediation decisions at the site. That evaluation is presented in this document. The primary COPCs at the site are TPH-d, TPH-g, and VOCs (including BTEX, fuel oxygenates, and naphthalene) related to suspected releases from former diesel and gasoline USTs. The proposed approach to pilot testing includes volatilization with direct injection of air to the subsurface, enabling a phase transfer of petroleum hydrocarbons and related compounds adsorbed to soil and dissolved in groundwater to a vapor phase. The air and vapors are then vented to the surface through the unsaturated zone. AS/SVE is achieved by injecting air directly into the aquifer and extracting the air and contaminant vapors under negative pressure through SVE wells, mitigating the vapor plume in the unsaturated zone. HVDPE wells were installed and screened through the vadose zone and the contaminant plume in groundwater. HVDPE removes a combination of contaminated groundwater and soil vapors from the subsurface, to be treated and collected for disposal. It creates a pressure gradient towards the DPE wells via use of vacuum, thus enhancing groundwater and soil vapor recovery. 1.3.1. Soil Vapor Extraction For SVE, a vacuum is applied to the soil matrix to create a negative pressure gradient that causes movement of vapors toward extraction wells. Volatile constituents such as petroleum hydrocarbons and related constituents can readily be removed from the subsurface through the extraction wells, and the extracted vapors are treated at the surface. Two key parameters used to determine if SVE could be a viable alternative for remediating hydrocarbon -impacted soils are the permeability of the soil and the volatility of the contaminants of concern (in this case petroleum constituents). When these parameters are favorable for SVE at a site, a treatability study can be implemented to investigate the effective ROI beneath the site, evaluate vapor - phase concentrations and hydrocarbon mass removal rates, and obtain engineering design parameters for determining appropriate equipment capacities for potential site -wide remediation. The SVE treatability study was intended to determine the ROI for soil vapor extraction in soils impacted with petroleum hydrocarbons and related constituents above groundwater in the source area (former USTs area). The number and depth of proposed SVE wells and associated monitoring points were selected to maximize data acquisition from various portions of an approximately 30 feet of impacted soil in the vadose zone. Each portion was tested separately. 1.3.2. Air Sparge Testing AS technology is implemented to reduce concentrations of volatile constituents in petroleum hydrocarbons that are adsorbed onto soils and/or dissolved in groundwater. The technology involves injecting contaminant -free air into the saturated zone, with the objective of transferring petroleum hydrocarbons and related volatile constituents from a dissolved phase to a vapor phase. The air is then vented through the unsaturated zone. OTI E