18-Env-B4 Site Assessment and Remediation · December 2019
Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
National Exams — December 2019 — 18-Env-B4: Site Assessment and Remediation (3 hours, open book). Instructions: answer FOUR of the FIVE Section A questions and ONE of the TWO Section B questions; all eight questions (A-1–A-5, B-1, B-2) are answered in full below as a complete study resource. Each question is worth 20 marks.
Reference texts: Nyer, E.K., Practical Techniques for Groundwater and Soil Remediation; Fetter, C.W., Contaminant Hydrogeology (2nd ed.); Leeson, A. & Hinchee, R.E. (1997), Soil Bioventing: Principles and Practice; CSA Z768-01, Phase I Environmental Site Assessment; British Columbia Contaminated Sites Regulation (Environmental Management Act); Ontario Regulation 153/04 (Records of Site Condition); Canadian Council of Ministers of the Environment (CCME), National Classification System for Contaminated Sites and Canada-Wide Standard for Petroleum Hydrocarbons in Soil; Karickhoff, S.W. (1981), organic-carbon partitioning correlations.
Question text not reproduced: the examination questions are © Engineers and Geoscientists BC. Open the official past paper (linked at the top of this page) to read the question, then follow the worked solution below.
Would I consider it? Yes, conditionally. For a site contaminated with a heterogeneous mix of hydrocarbons, PAHs, and heavy metals, in-situ biological or chemical treatment is poorly suited to the metals fraction (metals are not destroyed by biodegradation, only immobilized or extracted), which pushes the practical choices toward excavation-based remedies regardless. "Dig and dump" (excavation and off-site disposal) is a defensible choice when the schedule is tight, the contaminated volume is moderate and well-delineated, and a permitted disposal facility is reasonably close — but it should be weighed against ex-situ treatment/reuse alternatives (soil washing for metals, thermal desorption for PAHs) case by case rather than adopted by default.
Merits. Fast and schedule-predictable compared to in-situ treatment trains that can take months to years; effective on mixed-contaminant, heterogeneous soils (metals, PAHs, and hydrocarbons together) where no single in-situ technology addresses all three; transfers the contamination off-site to a facility engineered and permitted to contain it, immediately removing the on-site source and simplifying the site's own long-term liability profile; and allows the site to be brought to a verifiable, sampled end-state (backfilled and confirmed clean) quickly, supporting a fast redevelopment timeline.
Challenges. Excavation and haulage/tipping-fee costs scale directly (and expensively) with volume, and can exceed in-situ treatment cost once volumes are large; significant truck traffic and the associated GHG emissions and community disruption; the contamination is relocated, not destroyed — it becomes another facility's long-term liability, which is an environmental-equity consideration worth flagging explicitly; excavation below the water table requires dewatering and shoring, adding cost and its own environmental management burden (treated/discharged water); waste soil must be characterized and manifested correctly for disposal (hazardous vs. non-hazardous classification under provincial waste regulation, informed by the Canadian Environmental Protection Act framework for hazardous waste); and dig-and-dump addresses only the source soil — if a dissolved-phase groundwater plume has already migrated beyond the excavation footprint, it is not addressed and separate management is still required.
Is a RSC required post dig-and-dump? Yes. Removing the contaminated soil does not by itself discharge the regulatory requirement to demonstrate the property meets the applicable standard for its intended use before a change of use/redevelopment proceeds. Confirmatory soil (and, where relevant, groundwater) samples from the excavation base and sidewalls must demonstrate compliance with the appropriate site condition standards, and that confirmatory dataset is what supports filing a Record of Site Condition (Ontario) or equivalent certificate of compliance (BC's Contaminated Sites Regulation) — the RSC/certificate is the regulatory record of the "clean" end-state, not an optional formality that excavation bypasses.
