This paper describes thermal conduction heating of a trichloroethylene (TCE) source zone within vadose zone soils consisting of glacial till at depths of 50 to 125 ft below an active manufacturing facility. The performance objectives and metrics used to determine remediation success are presented. Access limitations inside the facility prevented traditional spatial soil confirmation sampling, which made performance assessment a unique challenge. Instead, the project team developed an approach utilizing multiple lines of evidence to document remedy completeness. These lines of evidence included achievement of target temperatures within the treatment volume, demonstration of asymptotic vapor concentrations extracted from the treatment volume, achieving modeled energy input goals, and verifying TCE concentrations in post-treatment soil samples collected at the few accessible locations within the operational facility. The treatment volume was divided into three discrete treatment areas or heating groups, each constructed and heated independently in order to meet an aggressive project schedule. Additionally, each line of evidence was required to be met in each group. After approximately 283 days of heating, temperatures exceeded 90 °C at 95% of the temperature monitoring points, TCE levels had diminished to asymptotic levels in the recovered vapors, and mass removal rates from the treatment volume declined to minimal levels. Confirmatory soil sample results indicated that average TCE concentrations achieved were more than an order of magnitude below the remedial goal of 1 mg/kg.

中文翻译：

---

125 英尺深 TCE 源的热传导加热 - 用于验证补救目标的多条证据

本文描述了对由活跃生产设施下方 50 至 125 英尺深度的冰川耕作组成的渗流带土壤内的三氯乙烯 (TCE) 源区进行热传导加热。提出了用于确定补救成功的绩效目标和指标。设施内部的访问限制阻碍了传统的空间土壤确认采样，这使得性能评估成为一个独特的挑战。相反，项目团队开发了一种利用多方面证据来记录补救措施完整性的方法。这些证据包括在处理体积内达到目标温度、演示从处理体积中提取的渐近蒸汽浓度、实现建模能量输入目标、验证在运营设施内少数可到达地点收集的处理后土壤样品中的 TCE 浓度。处理空间被分为三个独立的处理区域或加热组，每个处理区域或加热组都是独立建造和加热的，以满足紧迫的项目进度。此外，每组都需要满足每一条证据。经过大约 283 天的加热，95% 的温度监测点温度超过 90 °C，回收蒸汽中的 TCE 水平已降至渐近水平，处理体积的质量去除率降至最低水平。土壤样本验证结果表明，所达到的平均 TCE 浓度比 1 毫克/千克的补救目标低一个数量级以上。