Theme: 01. Remediation Technology Innovations

Topic Area: 01i. In Situ Chemical Oxidation: Optimized Design Approaches and Lessons Learned

Formatted Title:

A Comprehensive Design Approach to a Multicontaminant, Multireceptor Site

Background/Objectives:

Background/Objectives. From approximately 1964 to 2008, operations at the former Safeguard Chemical Facility (located in Elizabeth, New Jersey) included the manufacturing, filling (of aerosol containers), and distribution of aerosol products. During this time, household and industrial cleaners, polishes, deodorizers, insecticides, disinfectants, lubricants, and adhesives were produced at the Site. The bulk chemicals consisted of pesticides, solvents, and propellants, which were stored at the Site in aboveground storage tanks. There was an ongoing series of remedial investigations and remedial actions beginning in 1994, which identified chlorinated volatile organic compounds (cVOCs) and pesticides as the primary contaminants of concern in subsurface soil, groundwater, surface water, and sediments. To address upland contamination and protect sensitive receptors, GZA proposed a treatment train approach consisting of in situ injections at the hot spots to reduce source zone contaminant levels, followed by monitored natural attenuation (MNA) and removal of DNAPL using large-diameter caissons and drilling.

Approach/Activities:

Approach/Activities. Prior to initiation of the remedial efforts, several data gaps and design elements needed to be completed, including:

Complete the delineation of VOC, pesticide, and PCB contamination in subsurface soil and groundwater;
Design an approach to address DNAPL-saturated soils approximately 16 feet beneath the water table;
Perform treatability and bench-scale studies to design full-scale groundwater injections;
Identify potential offsite sources of contamination; and,
Design an environmentally sustainable remedial action that utilizes a diverse range of remedial technologies.

To achieve project objectives, several rounds of soil and groundwater delineation were conducted because the contamination was found to be more widespread than previously reported. To complete this effort and reduce the need for further delineation, additional tools were utilized to establish site-specific standards including SESOIL, SPLP analysis, and compliance averaging. Four (4) hot spots were delineated during the investigation, including one hot spot where elevated levels of PCE were detected at 3,000,000 ppm. A treatability study was conducted to select the appropriate amendments to address dissolved VOCs and pesticides. Fenton’s reagent (FR), sodium persulfate activated with carbohydrate and sodium hydroxide, and EZVI were evaluated during the study. This study indicated that a combination of FR and sodium persulfate was most effective in treating contamination at the Site. This combination of amendments was used to design the loadings of full-scale injections within three (3) targeted VOC and pesticide hot spots.

In situ injections were not designed in the fourth hot spot where elevated levels of PCE were detected at 3,000,000 ppm; the contamination in this hot spot was detected in a limited area and the volume of amendments estimated to treat the contamination would have mobilized the contamination off site. Therefore, a limited excavation using caisson rigs is proposed to address the DNAPL hot spot which will eliminate the need for costly support of excavation and sloping of excavation side walls.

Results/Lessons Learned:

Results/Lessons Learned. Two injection events were conducted in the dissolved hot spot areas and progress was monitored through geochemical parameters, soil sampling, and groundwater sampling. Following the first injection event, mobilization of absorbed contamination resulted in increases of dissolved fractions – hydrogen peroxide mobilized the adsorbed contamination, and sodium persulfate oxidized the desorbed fraction. The second injection event resulted in an overall mass reduction of 30% of dissolved cVOCs in groundwater, and upwards of 90% removal of PCE soil mass contamination.

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Morgan McBride

Biography