GEOSCIENCE AND ENVIRONMENTAL SERVICES

Case Study – Brownfield Services

Case Studies – Brownfield

Our staff have been heavily engaged in brownfield work in western and central Canada and abroad. We have completed several Environmental Site Assessments Phases I, II and III (Stages I and II Preliminary Site Investigation (PSI) and Detailed Site Investigations) within different environmental settings, including agricultural, urban, commercial and industrial property sites and particularly at mining, petrochemical facilities and also in the upstream oil and gas well sites. More often than not, the investigations entailed working in and around existing plants and operations. As such we are very conversant of the interfaces requirements and procedures to follow in conducting studies of this nature.

Plate 1. Drilling in progress in PSI Stage 2 investigation to collect soil samples for visual inspection, OVA screening and laboratory analysis.

At most of these sites, our activities focused on delineating areas of soil and groundwater contamination related to historical or on-going onsite activities and secondly to the regular monitoring of the shallow groundwater quality. In the Okanagan Valley in south-central British Columbia, one of our staff was fully responsible for the design, execution and oversight responsibilities in the implementation of numerous Stages I and II Preliminary Site Investigations (PSI) and Detailed Site Investigations at various brownfield sites including a former gas station that has been converted into a commercial property. The main objective of this particular investigation was to determine the presence or likely presence of potential contaminants of concern in the soils and groundwater systems beneath the property and adjoining ones and thereby determining the environmental liability, if any, associated with the property prior to transfer of ownership.

Plate 2. A contaminated soil band (dark- gray) visually identified in the drilled role during the PSI Stage 2 drilling event.

A a drilling rig were used to advance the holes downward (Plate 1). The various lithologies intercepted were logged in the process. The PSI Stage 2 activities on this project included visual observation and field screening of soil samples using an Organic Vapour Analysis (OVA) instrument to identify contaminated soil bands during hole advancement (Plate 2). Based on visual inspection and OVA screenings, grab and composite soil samples were selected and submitted to an accredited laboratory in British Columbia for analysis. Evaluation of site contamination was derived from the analysis and interpretation of the laboratory analytical results and field studies. The final site assessment report contained all contaminants of concern identified during the site investigations and also a detailed Conceptual Site Model, which clearly delineates areas and horizons of soil contamination on the property. The report also included entire sections that provided detailed narrative on the findings of the investigation.

Plate 3. A MEK Staff supervising hydrovacing of a shallow soil layer at an Oil and Gas compressor facility in Western Canada. This soil excavation exercise was carried out close to onsite utility lines, requiring care that the utility lines are not compromised during the follow-up drilling of a borehole.

Plate 4. MEK Hydrogeologist overseeing the follow-up intrusive sampling that was carried out as part of a Stage 2 Detailed Site Investigations at the Oil and Gas facility in British Columbia, Canada

Our Stage II PSIs and Detailed Environmental Site Investigations will usually entail the drilling of boreholes and construction of monitoring wells to determine the environmental quality of the surficial soil formation and shallow groundwater using hydrovac machines and drilling rigs (Plates 3 and 4). Initially the hydrovac machine is used to remove soils within the shallow horizon and thereby exposing the locations of utility lines within the area of investigation. Once these utility lines are exposed, borehole drilling is then advanced using a drilling rig. The hydrovacing ensures that utilities lines are not damaged during the intrusive sampling MEK staff have designed and constructed many groundwater monitoring networks and have planned and executed several monthly, quarterly and semi-annual groundwater monitoring sessions to determine groundwater quality, flow pattern and the long-term trends or changes in the groundwater quality at brownfield sites. (Plate 5).

Plate 5. A nested pair of monitoring wells under development prior to sampling for laboratory analysis

We have also developed (from our Stage II PSI and Detailed Site Investigations) several two- and three-dimensional groundwater flow models and “fence” diagrams that have enabled us to have in-depth understanding of the subsurface stratigraphy and interpreted the groundwater flow pattern at our facilities of interest (Plates 4 and 5). These understanding have been very invaluable in modeling contaminant transport and fate on our projects and also in developing comprehensive remedial action plans.

We Detailed Site Investigations) several two- and three-dimensional groundwater flow models and “fence” diagrams that have enabled us to have in-depth understanding of the subsurface stratigraphic sequence l and interpret the groundwater flow pattern at our facilities of interest (Plates 6 and 7). These understanding have be very invaluable in modeling contaminant transport and fate on our projects and also in developing comprehensive remedial action plans.

Sin-título-131

Plate 6. A three-dimensional contour plot superimposed on a fence diagram showing groundwater level within the various rock units.

Groundwater-1

Plate 7. A three-dimensional model of shallow groundwater flow pattern at an industrial site showing recharge and discharge areas (vertical scale exaggerated).