A 104-hectare (257 acre) property in Frisco, Texas in the Dallas-Fort Worth area, consisting of a former industrial recycling site and its surrounding buffer zone, now has excellent prospects for further community use.
Remediation work by Golder has helped the buffer property (surrounding the former Exide Technologies Frisco Recycling Center) to be sold to a City of Frisco development agency that is planning its future productive use. Golder is also involved in the design of remediation work on the former industrial property inside the buffer zone.
To date, we have performed several field investigations, completed field oversight and reporting for an approximately 18-month remediation field program in the undeveloped buffer zone property portion of the site; and designed the remedial program for the former operating plant portion of the site.
Golder proposed a three-part remediation program for the former industrial site.
Funnel and gate treatment for impacted groundwater
We considered several alternatives to deal with groundwater issues, including the presence of the metals, lead, cadmium, arsenic, and antimony. Based on the site conditions and geology, as well as evaluations for performance, effectiveness, implementability, schedule and cost, we delivered a proposed remediation solution involving several innovative and proven technologies.
This proposed solution starts with a zero-valent iron (ZVI) funnel and gate permeable reactive barrier (PRB). Implementation involves digging a continuous trench across the path of the contaminated groundwater (gate) and filling that trench with reactive materials including ZVI, through which the groundwater must flow. Groundwater flow through the “gate” reduces the metal impurities in the groundwater. Laboratory column studies (tests using groundwater at the site with the ZVI) were performed by Golder to show the effectiveness of this proposed solution.
Slurry walls will be installed to funnel the impacted groundwater towards the PRB. These underground “walls” will be built by digging trenches and filling the trenches with impermeable materials to funnel the impacted groundwater into the barrier or gate.
A staged approach to sediment remediation
We also addressed potential contamination of the sediment in a perennial creek that flows through the property. We started by finding out more about the creek, through sediment characterization, ecological and human health risk assessment, and establishing the site-specific background concentrations of arsenic.
With this information at hand, we recommended a staged approach to sediment remediation. The approach includes setting priorities so that target areas can be remediated first. Other sediment in the creek will be evaluated to determine areas for additional excavation using new data (to be collected at the time of remediation) and an approved exposure point concentration methodology.
In this way, the remediation work was targeted, so areas of greatest concern are remediated first to minimize impacts to the general creek environment – while also protecting the surrounding environment and human populations.
To help the property owners implement the steps needed to remediate the site, we prepared the Part B Permit Renewal Application for the site to meet the requirements of the Texas Resource Conservation and Recovery Act. The permit application includes a Response Action Plan that outlines the planned remediation at the site as well as the design and closure of one existing and one new Corrective Action Management Unit at the site.
Soil remediation, consolidating and capping
The third part of our program involves consolidating the impacted soil and sediment within the former industrial site so that they can be safely managed.
Once the impacted soil and sediment have been consolidated in one place, they will be covered with a multi-layer engineered cap consisting of a geosynthetic clay liner, a layer of geomembrane, and clean soil to prevent contact with humans and wildlife. The cap will also prevent erosion and surface water infiltration. The new ground surface will then be vegetated to reduce the potential for erosion and will improve the site’s appearance. This, we believe will be a cost-effective remedy, with a lower carbon footprint than would be produced by trucking the soil and sediment off-site or implementing other potential remedial options.
The result will be a sustainable, low-maintenance solution that protects the environment and the general public.