Question 1 of 8: Site Assessment for a Former Plating Facility

Question A-1: Site Assessment for a Former Plating Facility (20 marks)

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.

The bank’s request is a classic pre-sale environmental due-diligence trigger, and the plating/wastewater history (chrome, zinc, silver; 4 concrete process tanks; an unlined onsite sludge lagoon) is a textbook source of hexavalent chromium, zinc and cyanide contamination in soil and groundwater. The property’s own geometry — a creek along the entire west boundary, a lagoon and treatment plant roughly in the middle of the site, and a municipal groundwater supply serving the surrounding residential area — means the assessment has to characterize both an on-site source and two credible off-site receptor pathways (the creek, and the aquifer feeding the municipal wells) before residential re-use can be certified.

Step 1 — Phase I Environmental Site Assessment (ASTM E1527). A records/historical review (fire insurance maps, aerial photography, prior ownership and permits, spill/incident reports, regulatory database search for the site and adjoining properties), a site reconnaissance (walkover looking for staining, stressed vegetation, stained concrete around the four tanks and the lagoon berm, drums/tanks left in place, floor drains), and interviews with prior operators/regulators. The output is a Recognized Environmental Condition (REC) list — here the four process tanks, the unlined sludge lagoon, and any former underground piping between them are the obvious RECs; the arterial road 200 m south is not a REC for this site. Phase I alone cannot support a “clean” determination once RECs this specific exist — it defines where Phase II sampling must go.

Step 2 — Conceptual site model. Before drilling, build a CSM from the Phase I findings: source areas (tanks, lagoon), the sandy-loam soil (moderate-to-high permeability, favouring vertical infiltration and lateral groundwater transport rather than retarding contaminants), and two receptor pathways — lateral flow west ~50–250 m to the creek, and whatever direction the water-table gradient actually runs toward the municipal wellfield. The CSM is what turns “test everywhere” into a defensible, targeted Phase II design.

Step 3 — Phase II Environmental Site Assessment (ASTM E1903). Intrusive investigation targeted at the RECs: soil borings immediately around and beneath the four concrete tanks and any connecting trenches (checking for tank-floor cracking and leakage), a dense grid of borings/test pits through the lagoon footprint and its berm (lagoons routinely leak through the base long before visible failure), and at least one background/upgradient boring outside any plausible influence to establish site-specific soil chemistry. Groundwater monitoring wells are installed on a triangulated network bracketing the source areas, with at least one well between the lagoon/tanks and the creek (verifying whether the creek is a receptor or, in dry periods, a source of dilution) and one or more wells on the inferred line toward the residential wellfield. Analyze soil and groundwater for total and hexavalent chromium, zinc, silver, total/free cyanide (common in plating rinse baths), pH, and any solvents used in degreasing lines. Compare results to the applicable generic or site-specific numerical standard for the intended land use (residential/parkland, per the province’s contaminated-sites regulation).

Step 4 — Delineate and risk-rank. Where standards are exceeded, step-out borings define the lateral and vertical extent of the plume, and the CSM is updated with real gradient and flow-direction data (not assumed) to confirm or rule out migration toward the creek and toward the municipal wellfield 1 km away. Because the community draws its water supply from the same local aquifer, even a low-probability pathway to the wellfield is a material finding for the bank and must be explicitly assessed, not waved off on distance alone.

Step 5 — Report and remedial options. Summarize findings against the residential-use standard, and if exceedances are confirmed, outline remedial options (excavation/off-site disposal of lagoon sludge and impacted soil around the tanks, pump-and-treat or monitored natural attenuation for any groundwater plume) with order-of-magnitude costs, so the bank can weigh remediation cost against sale value — the deliverable the whole assessment exists to support.