WORK PLANS - Laserfiche WebLink

Home Browse Search

11 4.2 Air Spar in with SVE g g Air sparging and SVE are two technologies that have been proven successful in their application to in-situ treatment of subsurface soil and groundwater contaminated with TPH-g and BTEX. Air sparging is primarily used for groundwater remediation, while SVE is used for vadose zone soil treatment. Integrated together, these two technologies form an alternative that is considered potentially applicable for the site. ' In principle, the air sparging process involves the use of pressurized air to remove volatile contaminants from groundwater by means of "stripping" (as in air stripping). To implement air sparging at this site, air would be injected under pressure into the saturated zone to enhance volatilization of TPH-g and BTEX. An air compressor would be used to provide the pressurized air. Under the pressure gradient, the hydrocarbons "stripped" from the water phase into vapor phase would be driven, along with the air, from the saturated zone into the vadose zone. With a SVE system running simultaneously, the hydrocarbons in the vadose zone would then be drawn into the vapor extraction wells by the moving soil air under vacuum. In addition to 1- to 2 -inch diameter air sparge wells or points, the air sparging system would consist of an air compressor and probably a receiving tank of 120 gallons in capacity or equivalent. Steel piping would be used to convey compressed air from the compressor tank to the injection wells. The SVE system, on the other hand, would require 2- to 4 -inch diameter vapor extraction wells and include a blower or vacuum pump, a liquid -vapor separator, and an offgas emission control unit such as a catalytic thermal oxidizer. The emission control requirement would be essentially the same as in the case of pump -and -treat where an air stripper would be used. Plastic piping would usually be used to convey captured soil vapor from the vapor extraction wells to the blower or vacuum pump. Since SVE had previously been conducted at the site to remove TPH-g and BTEX from the vadose zone, an SVE test would not be necessary. A field pilot test of air sparging would, however, be recommended for proper sizing of the air sparge system for full-scale treatment. The test data would also be used to further assess if the site subsurface conditions would favor the implementation of air sparging for groundwater treatment. 4.2.1 Technical Effectiveness Air sparging coupled with SVE has the capability of reducing the dissolved phase mass of TPH-g and BTEX in groundwater at the site — meeting the primary treatment objective in bulk mass reduction. However, as in the case of pump -and -treat, its effectiveness will be limited due to the presence of the relatively low permeable silty to clayey soils within the treatment area. Even though the TPH-g and BTEX in the gravelly, sandy soil layers would be "stripped" out L I FS Onsite Petroleum Hydrocarbon Remediation.doc 4-4 Shaw Environmental, Inc.