Question 2 of 4

Question 2 (25 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.

(a) Desk Study

The desk-study section of the report should cover the regional and site geology (bedrock and surficial units, structural setting), site history and prior land use (from historical air photos and fire-insurance/city directory records — critical for flagging contamination or old fill), existing subsurface information (prior geotechnical reports, water-well database records for the area, utility as-builts), topography and drainage, seismicity/regional hazard context, and a statement of the regulatory and code framework the project falls under. It should conclude with a preliminary ground model and the specific data gaps that the field program is designed to close, so the reader can see the logical link from desk study to the exploration plan that follows.

References/sources: provincial and Geological Survey of Canada bedrock/surficial geology maps; provincial terrain and soil survey mapping; historical topographic sheets and air photo archives (National Air Photo Library); provincial water-well database and prior geotechnical report archives held by the local authority having jurisdiction; municipal utility records; NBCC seismic hazard data.

(b) Site Reconnaissance

This section should record what a walkover of the actual site revealed and confirms or contradicts against the desk study: surface expression of geology (outcrop, evidence of fill or disturbed ground, seepage/springs, ponding), access and constructability constraints for the planned field equipment (overhead/underground utilities, slope, vegetation, working room), existing structures and their apparent condition (cracking, settlement evidence relevant to a differing-site-conditions baseline), environmental observations (staining, odour, vegetation stress suggesting contamination), and photographs keyed to a site plan. It should end with any changes the reconnaissance triggers to the planned field program (borehole relocation, added test pits) — the reconnaissance is a check on the desk study's assumptions, not a formality.

References/sources: the desk-study ground model itself (to know what to look for); one-call/utility locate services before any physical marking or probing; municipal zoning and property records for access; provincial contaminated-sites registry if prior industrial use is suspected.

(c) Ground Investigation

This is the field/laboratory program itself and should report: the exploration methods used and why (boreholes, test pits, CPT, geophysics) with their locations shown on a plan and cross-referenced to a coordinate/elevation datum; borehole/test-pit logs summarizing stratigraphy, sampling, and in-situ test results at each location; the laboratory testing program and a summary of index and strength/consolidation results; groundwater observations (standpipe/piezometer levels, any artesian conditions); and an interpreted subsurface profile (plan and cross-section) tying the discrete exploration points into a continuous ground model, with an explicit statement of confidence/limitations between exploration points.

References/sources: CFEM 4th ed. (governing Canadian standard of practice); relevant ASTM standards for each method used (D1586 SPT, D1587 tube sampling, D5778 CPT, etc.); provincial professional-practice guidelines for geotechnical reporting; the desk study for context against which the field results are checked for consistency.

(d) Selection of Exploration Methods

This section should justify, not just list, the chosen methods against the ground conditions anticipated from the desk study and the specific parameters the design needs: boreholes with sampling where undisturbed or index samples are required for lab testing; CPT where a rapid, continuous, cost-effective profile is wanted in soil that will accept a pushed cone (not gravelly or bouldery ground, and not rock); test pits where large-diameter or shallow bulk sampling and direct visual logging is valuable and the depth is safely achievable; geophysics (seismic refraction, resistivity, ground-penetrating radar) where a rapid areal picture of a bedrock surface, void, or contaminant plume is needed to target the more expensive intrusive methods efficiently; and in-situ testing (field vane, pressuremeter) where the parameter needed cannot be reliably obtained from a disturbed or even a good-quality tube sample. The selection should also explicitly address exploration spacing/depth (driven by structure loads and footprint, and by the ground's expected variability from the desk study) and any access or environmental constraints (contaminated ground requiring special handling, working over water, restricted headroom) that rule specific methods in or out.

References/sources: CFEM 4th ed. Ch. 3 (exploration method selection guidance by ground condition); manufacturer/industry equipment capability data (CPT push capacity, rig access requirements); relevant ASTM method standards; prior local experience/precedent from the desk study's archived reports for similar ground in the area.