Cost and Performance Report for the Pilot-Scale Permeable Barrier at Former Naval Air Station Moffett Field Mountain View, California

摘要

A pilot-scale permeable reactive barrier was installed at Moffett Field in April 1996 and its performance was monitored over the following 16 months on a quarterly basis. The details of this study are described in a technology evaluation report (Battelle, 1998). This document provides a brief account of the technology evaluation. The objective was to capture and treat-a small portion of the West Side Plume that contains chlorinated volatile organic compound (CVOC) contaminants primarily trichloroethene(TCE), cis-1,2- dicholoethylene (cis-1,2-DCE), and perchioroethene (PCE). The reactive cell in the funnel and gate type barrier is composed of granular zero-valent iron, a strong reducing agent. The geochemical evaluation included analysis of inorganic parameters in the barrier and its vicinity, as well as analysis of core samples of the iron collected at the end of 16 months of operation Calcium and iron compounds appear be precipitating out in the reactive cell However, the actual calcium precipitate mass found on the iron cores was much lower than the loss of dissolved calcium in the groundwater flowing through the reactive cell. This may indicate that not all the precipitates formed-stay in the gate; colloidal-sized precipitates could be flowing out with the groundwater. There were no indications,at the end of 16 months, of any impending decline in the reactivity or hydraulic performance of the barrier. The barrier operated unattended and without maintenance after construction. The only recurring cost would be for compliance monitoring. If the barrier retains its performance over approximately 5 years, indications are that it will be more cost-effective than a groundwater pump-and-treat system.