A Case Study of Aquifer Air Sparging for Remediation of LNAPL

摘要

Aquifer air sparging is a well established and cost-effective remediation technology for dissolved-phase contamination. However, it has historically been discouraged for remediation of large amounts of light non-aqueous phase liquids (LNAPL) due to the potential for mobilization and spreading of contamination during pressurized air injection. To challenge the precautions stated in the literature, a systematic approach of intact soil core sampling, lateral LNAPL mobility analysis, pilot testing, full-scale operation, and laser-induced fluorescence (LIF) survey was performed. This study was performed at a large JP-4 and JP-8 jet fuel release site for which air sparging and soil vapor extraction (SVE) was identified as the most cost-effective option for remediation.rnThe site lithology consists of fine- to medium-grained sand throughout the target treatment zone which extends to a depth of 72 feet below ground surface. The water table has historically fluctuated between 32 to 50 feet below grade, in response to hurricane and drought cycles and has created an extensive LNAPL smear zone. The LNAPL smear zone submergence and in-well LNAPL thicknesses (up to 3 feet) are highly variable depending upon the local drought conditions.rnIntact soil core samples were collected to assess the range of potential lateral LNAPL mobility under air sparge induced conditions prior to pilot testing. The results showed extremely small mobility and low risk for LNAPL spreading. Subsequently, an air sparging/SVE pilot test was successfully performed and full-scale construction followed shortly thereafter. A second round of post-full-scale startup intact soil core sampling and a LIF survey were conducted. The weight of evidence collected indicates that LNAPL has not spread and, in fact, indicates that the LNAPL is being remediated. This presentation will present data illustrating the effectiveness of air sparging/SVE alone for treatment of the LNAPL.