Formatted Title
Obtaining a Remediation Certificate Using a Multifaceted Approach to Site Cleanup
Background/Objectives
A Remediation Certificate was obtained with a multifaceted treatment approach, using both in situ injection techniques and excavation, within two years for a particularly challenging active industrial site in Alberta, Canada. The site had previously employed a multi-phase extraction (MPE) system over five years which was removed in 2005 as it was inefficient.
This site went through many stages and changes: evaluation and implementation of MPE, evaluation and removal of MPE, Phase I and II assessments, change in owner priority (desire to sell), and various options to reach the goal of Tier 2 remediation closure and sale.
Geo Tactical Remediation Ltd. (Geo Tactical) was engaged directly by the property owner for an alternate option to excavation (the only way to remediate the site within one year, which was the property owner's intent). The owner did not pursue the excavation due to ethical concerns about hauling 5,500m3 of soil. Geo Tactical proposed in situ chemical oxidation (ISCO) over two years (no excavation), which was significantly lower in cost (<50% of the initial excavation estimate). The remedial action plan for site-specific Alberta Environment of Sustainable Resource Development Tier 2 criteria (no domestic use aquifer, no aquatic receptors, no rezoning) was submitted and approved in 2010.
Approach/Activities
The geology consists of low permeability soils (1x10-6 m/s) requiring fracture injection to emplace remedial amendments. The contaminated soil extent was 1,700 m2, a total treatment volume of 5,500 m3 and the groundwater extent was 2,900 m2.
The treatment included a multifaceted approach with in situ amendment emplacement and ex situ excavation (900 tonnes). The original program did not include excavation, but a hotspot was later located and would add significant time to the project if treated by ISCO. Geo Tactical also identified F2s, which had not been detected previously, during further delineation of the hotspot and sampling. An iterative approach to treatment based on each injection and sampling event helped identify areas of concern like the hotspot and other unknowns while effectively emplacing amendments.
The amendments used on site were sand proppant, surfactant, hydrogen peroxide, calcium peroxide, sodium persulfate, and sodium hydroxide. The amendments were emplaced by in situ: fracture injection, permeation injection, passive treatment via slow-release oxygen diffusers, and oxidant canisters.
Results/Lessons Learned
This site is an example of effective adaptive site management and strategy. The iterative approach allowed for adjustments on site to previous unknowns, allowing all parties to adapt together to reach the end goal of the property sale and the Remediation Certificate. The project began in 2011 and ended in 2013.
The Remediation Certificate was issued in October 2014.