Hoffmann-La Roche Inc., 102 pp, 2020

This report presents 3- and 6-month post-injection results of enhanced in situ bioremediation (EISB) to remediate groundwater contaminated with PCE+ (PCE and its degradation products) at IA-6. ABC^® electron donor; TSI DC^® Dehalococcoides ethenogenes bioaugmentation culture; sodium ascorbate, sugar, and yeast to create anaerobic conditions; and pH buffer was injected into source area injection wells. Injection was combined with recirculation to facilitate the amendment transport and distribution within the treatment zone (taken from the April 2019 Interim Remedial Measure Progress Report). July 2019 sampling results indicated that concentrations of PCE and its degradation products were below the groundwater quality standards (GWQS) at eight of the 13 wells within the treatment zone. One or more of the target PCE+ constituent concentrations were above GWQS at the remaining five wells within the IRM treatment zone but were mostly only slightly above GWQS. The effectiveness of EISB for the remediation of PCE in groundwater throughout the targeted treatment area was demonstrated through multiple lines of evidence including biodegradation of PCE into daughter products to below GWQS, the presence of VC as the primary PCE degradation product, individual target constituent trends that showed evidence of biodegradation of PCE>daughter products>ethene and ethane, and the presence of anaerobic and reducing geochemical conditions necessary to support ongoing biodegradation. https://www.roche-nutley.com/content/dam/roche-nutley/en/documents/RocheNutley/IA6IRMProgRptMarch2020.pdf
The April 2019 Interim Remedial Measure Progress Report: https://www.roche-nutley.com/content/dam/roche-nutley/en/documents/RocheNutley/pdfs/gw_irm_apr_19/20190411_IA-6%20IRM%20Progress%20Report.pdf
To see updates for all IAs for the site, see https://www.roche-nutley.com/home/remediation-updates.html