18-Env-B4 Site Assessment and Remediation · May 2014
Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
National Exams — May 2014 — 04-Env-B4 / Site Assessment and Remediation. 3 hours duration; open-book exam (any non-communicating calculator permitted). The paper is split into Section A (five questions, candidates asked to answer three) and Section B (three questions, candidates asked to answer two), each question worth 20 marks. All eight questions are solved below for completeness.
Reference texts. Suthersan & Payne, Remediation Engineering: Design Concepts (CRC Press); Gavaskar, Gupta, Sass, Janosy & O'Sullivan, Design Guidance for Application of Permeable Reactive Barriers for Groundwater Remediation (Battelle/EPA, 2000); ASTM E1527 Standard Practice for Phase I Environmental Site Assessments and ASTM E1903 Standard Practice for Phase II ESA; Mercer & Cohen (1990), “A review of immiscible fluids in the subsurface,” Journal of Contaminant Hydrology; Freeze & Cherry, Groundwater; Davis & Cornwell, Introduction to Environmental Engineering (6th ed.); Ontario Reg. 153/04 under the Environmental Protection Act (Record of Site Condition regime); BC Environmental Management Act — Contaminated Sites Regulation.
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 dry-cleaning tenant is one of the classic “special concern” business types flagged by ASTM/CSA Phase I due-diligence protocols, because PCE is a dense, non-aqueous phase liquid (DNAPL) that historically leaked from still bottoms, hose connections, and filter-cartridge disposal at thousands of strip-mall cleaners across North America. Two features of this site raise the stakes beyond a routine strip-mall assessment: the sandy loam under the parking lot is moderately permeable, so any historical spill at floor drains or the loading dock could migrate vertically with limited attenuation; and the community draws its municipal supply from local groundwater, meaning a confirmed release is not just an on-site liability but a potential threat to a drinking-water source, which will substantially affect both the underwriting decision and the regulatory response.
The assessment begins with a records review: historical aerial photographs and fire-insurance plans to confirm how long dry-cleaning has operated at the unit and whether other historically higher-risk tenants (gas station, auto repair) ever occupied the plaza; a search of the provincial contaminated-sites registry, waste-manifest and spill-report databases, and any prior Phase I/II reports on file; and a title search for restrictive covenants or prior remediation orders. This is followed by a site reconnaissance — walking the unit and the common areas for stained pavement, floor drains, sumps, PCE storage/still equipment, odours, and stressed vegetation — and interviews with the current operator, the property manager, and (where accessible) past operators, to establish operating history, equipment vintage, and any known spills. The Phase I report identifies Recognized Environmental Conditions (RECs): here, the mere presence of a PCE dry-cleaning operation on a permeable soil is itself a REC warranting further investigation, regardless of whether visible staining is found.
Because PCE is volatile as well as mobile, the Phase II program should combine sub-slab soil-vapour sampling beneath the dry-cleaning unit and adjoining units (to screen for vapour-intrusion risk to occupants) with soil borings at floor drains, the still/solvent-storage area, and the loading dock, advanced to and just below the water table to check whether DNAPL has reached groundwater. Groundwater monitoring wells should be installed both immediately downgradient of the unit (source-area compliance) and further downgradient toward the property line, given that DNAPL migrating past the water table can pool on any lower-permeability lens and continue to dissolve into groundwater for decades. All soil and groundwater results are compared against the applicable provincial numeric standards (e.g., BC Contaminated Sites Regulation or the equivalent CCME guideline) for both the direct-contact/vapour-intrusion pathway and — because the aquifer feeds the municipal system — the drinking-water pathway, which typically governs and is far more stringent.
The final deliverable to the owners/insurer is a report that (i) states whether a REC was confirmed and, if so, characterizes its lateral and vertical extent and concentration relative to standards; (ii) estimates the probable remediation liability and any ongoing risk-management costs (e.g., a sub-slab depressurization system, or long-term groundwater monitoring); and (iii) recommends underwriting terms — full coverage, a pollution exclusion, a higher premium, or coverage conditional on installing recommended controls. Because a municipal drinking-water aquifer is potentially affected, the report should also flag the regulatory notification obligations that would be triggered by a confirmed release, since these carry their own liability and timeline implications for the insurer.
