18-Env-B4 Site Assessment and Remediation · May 2013
Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
Reference texts: Davis & Cornwell, Introduction to Environmental Engineering, 6th ed.; Freeze & Cherry, Groundwater, 1979; Fetter, Contaminant Hydrogeology, 2nd ed.; LaGrega, Buckingham & Evans, Hazardous Waste Management, 2nd ed.; Suthersan, Remediation Engineering: Design Concepts, 2nd ed.; Leeson & Hinchee (AFCEE), Principles and Practices of Bioventing, 1997; CSA Z768/Z769 (Phase I/II ESA); BC Environmental Management Act & Contaminated Sites Regulation.
The paper instructs candidates to answer any THREE of the FIVE questions in Section A and any TWO of the THREE questions in Section B. All eight questions are answered in full below, since this solution set is used as a complete study resource.
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.
A condominium conversion is the most sensitive land use a former industrial parcel can be assigned, and the fact that the municipality's drinking water is itself drawn from local groundwater turns any residual contamination at this site into a potential source-water issue, not just an on-site risk. The assessment therefore has to be staged so that investigation effort is concentrated on the specific contaminants a metal-stamping operation is known to leave behind, and calibrated to the strictest applicable standard from the outset.
The first step is a Phase I Environmental Site Assessment (CSA Z768) — a non-intrusive desktop and reconnaissance study, not sampling. It reviews historical fire-insurance plans, aerial photographs, city directories and prior environmental reports to reconstruct the site's operating history (press location, hydraulic-oil reservoirs, degreasing baths, metalworking-fluid storage, any transformer or waste-oil pad), searches provincial and federal contaminated-sites registries for the parcel and adjoining properties, and walks the site for visual evidence of staining, stressed vegetation, or buried tanks. Metal stamping is a listed Potentially Contaminating Activity under BC's Contaminated Sites Regulation (Schedule 2), so a Phase I alone is enough to trigger a Site Profile filing with the Ministry of Environment before redevelopment can proceed. The output of this phase is a Conceptual Site Model (CSM) identifying Areas of Potential Environmental Concern (APECs) — press bays, the degreasing area, any floor drains and their historic discharge point, and fuel/oil storage.
Where the Phase I identifies APECs (the normal outcome for this type of facility), a Phase II ESA (CSA Z769) follows with a targeted intrusive investigation: soil borings and test pits placed directly at the identified source areas rather than on a uniform grid, sampled at multiple depths and analyzed for the RCRA-8 metals plus zinc and cadmium (stamping and plating fluids), petroleum hydrocarbons F1–F4, and chlorinated/aromatic solvents (degreasing agents such as TCE or PCE are common at this vintage of facility). Because the site is on clay, contaminant migration is expected to be slow and dominated by vertical seepage along desiccation cracks and fractures rather than by bulk lateral flow through the matrix — the investigation should specifically look for a perched water table above the clay and for preferential pathways (utility trenches, foundation drains) that can short-circuit the low bulk permeability. Groundwater monitoring wells are essential here, screened both in any perched zone and in the deeper aquifer that supplies the municipal wells, because a completed drinking-water exposure pathway is the single highest-priority finding this assessment could return.
Because the end use is residential, every result is compared against the BC Contaminated Sites Regulation's most stringent (urban park/residential) numerical standards, including the vapour-intrusion pathway for any chlorinated solvents recovered near where condominium units will be occupied — soil-vapour sampling should be added to the Phase II scope for this reason alone. If standards are exceeded, the site proceeds to a Detailed Site Investigation and a Remediation Plan, culminating in either a Certificate of Compliance or a risk-managed closure (engineered barriers, a vapour mitigation system, and/or a restrictive covenant on title) before the condominium can be occupied. Ongoing groundwater monitoring, tied to the municipal well field's capture zone, should continue through and after construction to confirm the drinking-water pathway remains protected.
