Theme: 03. Green and Sustainable Remediation

Topic Area: 3a. GSR Best Practices and Nature-Based Remediation Case Studies

Formatted Title:

Sustainable In Situ Remediation with Targeted Solids Emplacement for Expedited Brownfield Redevelopment: A German Case Study

Background/Objectives:

In urban areas, brownfield redevelopment projects oftentimes are carried out under tight deadlines. In the past, traditional remediation technologies such as excavation and offsite disposal or pump and treat have been employed because they require a limited amount of time to be designed and implemented but remediation activities may cause greater impact than the contamination that they intend to address. Green and sustainable remediation (GSR) technologies can substantially reduce the environmental footprint of remediation and maximize overall net benefits. Compared with traditional methods, they can typically reduce the life-cycle greenhouse gas emissions by ~50–80 % (Hou et al., 2023). The case study location is a large urban brownfield site that was previously used as a military installation. Re-zoning required the remediation of two shallow chlorinated hydrocarbon (CHC) groundwater impacts with contaminant plumes extending underneath significant stretches of the residential housing units currently under construction. The objectives of this case study were to

1. assess common GSR claims based on a real-case, full-scale, in situ remedy in Germany using a public-domain GSR assessment tool;

2. demonstrate the efficacy of a commercially available in situ amendment to achieve expedited site closure with brownfield redevelopment activities occurring in parallel.

Approach/Activities:

Targeted solids emplacement (TSE) technology was applied for full-scale treatment using Evonik’s EHC^® amendment to facilitate expedited brownfield redevelopment by one-time injection of 200 metric tons of amendment across a total source area of 6,500 m² (1.6 acres) using conventional direct push (DP) equipment over a course of seven months. EHC^®represents a mixture of recycled materials such as industrial (for the micro-scale ZVI) and agricultural waste (for the organic carbon component). A rigorous post-treatment groundwater sampling program has been implemented utilizing a large monitoring network to assess the efficacy of the remedy over the next three to five years. TSE remediation environmental footprint factors were compared to two conventional remediation technologies previously assessed (excavation and off-site disposal and pump and treat), including, amongst others, amendment product data, energy use and fuel consumption for on-site and off-site activities.

Results/Lessons Learned:

Several lessons were learned from the full-scale project such as that a single amendment injection may allow for achieving the stringent remediation goals of 20 µg/L CHC in treatment areas where the length of effectiveness was >20 months.

GSR metrics performance of TSE showed up to 86% less GHG emissions compared to the two conventional technologies assessed. At the time of abstract submittal, post-treatment monitoring was ongoing at the site and additional results are expected to be presented. CHC contaminants were virtually mineralized to ethene within a two-year time period, based on the results of extensive pilot test monitoring prior to implementation of the full-scale remediation.

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Michael Herbst