Difficult access conditions have limited techniques for groundwater system characterization and monitoring in bedrock exposed landscapes. This condition is common in the mining industry and resulted in the development of lightweight portable drills. This paper describes how these drills were used at a contaminated site to understand the groundwater flow system by adapting piezometer designs, ensuring effective seals to obtain reliable hydraulic head, hydrochemistry, and contaminant concentrations. Two drilling machines were evaluated: the Shaw Portable Core Drill (TM) fits in a backpack and can advance continuously cored rock holes, nominal 51 millimeters ( mm) diameter, to depths up to approximately 15 meters (m); and the larger Winkie Drill (TM) requires a two or more people to mobilize and can advance continuously cored holes, nominal 48 mm diameter, to depths of approximately 45 m. The resulting small diameter coreholes were accommodated in the design of each well using a seal created by injecting grout into a semipermeable fabric sleeve. This "fabric sleeve" serves as a means to contain the grout and ensures that the entire annulus above the screen is sealed without loss of grout into the formation, allowing the well to perform as a piezometer. To develop and demonstrate this methodology for groundwater monitoring in bedrock, the two drills were used in drainages located along the slopes of an elevated sandstone outcrop near Los Angeles, California. Unique insights into the groundwater flow system of this bedrock environment, which would otherwise be unattainable, were achieved. This methodology overcomes the accessibility limitations of conventional drilling methods that prevent installation of wells in remote and rugged mountainous terrains.

Understanding agricultural contamination in bedrock aquifers is challenging due to complexity of fracture networks and limitations in data acquisition imposed by instrumentation and drilling costs. Engineered assemblages known as multilevel monitoring systems (MLSs) maximize data from each borehole by providing numerous, depth-discrete monitoring intervals for profiles of hydraulic head and hydrochemistry. This article describes a hybrid MLS that uses key components of the Waterloo MLS, with extra piezometers of sufficient diameter to accommodate removable transducers for continuous pressure monitoring, attached to the outside using custom clamps. Monitoring intervals are created with sand packs separated by bentonite seals, either via backfilling from surface or tremie placement. The hybrid MLS is best suited for use in rotary drilled boreholes 12 to 15 cm diameter, smaller holes have insufficient space for the MLS and added piezometer(s) while larger holes have excessive backfill material and purge requirements. Variations were installed to 60 m depth in sandstone in Prince Edward Island, and to 150 m in dolostone in southwestern Ontario. Transducers in the external piezometers provided temporal head data under ambient and stressed conditions in key intervals, and manual measurements in all ports provided detailed vertical hydraulic snapshots. Combined with hydrochemistry profiles from groundwater sampling, the hybrid MLS provided detailed composite datasets for interpreting flow and transport in these bedrock aquifers. The hybrid MLS offers promise as a versatile low-cost option for groundwater studies in agricultural areas providing improved insights on groundwater flow systems and vertical distribution of nitrate and other contaminants, allowing more informed management decisions.

Use of direct‐push sampling tools fur rapid investigations of contaminated sites has proliferated in the past several years. A direct‐push device, referred to as a ground water sampling profiler, was recently developed at the University of Waterloo. This tool differs from oilier direct‐push tools in that point samples are collected at multiple depths in the same hole without retrieving, decontaminating, and re‐driving the tool alter each sampling event. The collection of point samples, rather than samples from a longer screened interval, allows an exceptional level of detail to be generated about the vertical distribution of contamination from each hole. The benefits of acquiring this level of detail arc contingent on minimization of vertical cross contamination of samples caused by drag down from high concentration zones into underlying low concentration zones. In a detailed study of chlorinated solvent plumes in sandy aquifers, we found that drag down using the profiler is minimal or non‐detectable even when the tool is driven through high concentration zones of dissolved chlorinated solvent contamination. Chlorinated solvent concentrations, primarily PCE and TCE at or below a detection limit of 1 μg/L, were obtained directly beneath plumes with maximum concentrations up to thousands of μg/L. Minimal drag down, on the order of a few μg/L to 20 μg/L, may have been observed below chlorinated solvent concentrations of several tens of thousands to hundreds of thousands of μg/L. Drag down through DNAPL zones was not evaluated.

A team of geologists and engineers conducted an investigation in a dense, non-aqueous phase liquid contaminant (DNAPL) source area at Pease Air Force Base (AFB) Installation Restoration Program Site 32. The investigation was designed to (1) demonstrate that vertical drive point profiling using techniques and equipment developed by the Waterloo Centre for Groundwater Research would work at this hydrogeologically complex site and (2) locate solute concentrations indicative of DNAPL. The original contaminant source at Site 32 was a 1,200-gallon (≅ 4500 L) underground storage tank with an overflow discharge pipe. The tank held waste solvents from aircraft maintenance in Building 113 at the former Pease AFB. The tank was removed in 1988. The overflow discharge pipe and contaminated soil under and along the pipe were removed in 1990. The results of the Site 32 Source Area Remedial Investigation/Feasibility Study indicate that solvent-related contaminants are present in soil and overburden and in bedrock groundwater and that there is a residual DNAPL source resulting in dissolved-phase groundwater contamination. Efforts to locate DNAPL using monitor wells have been unsuccessful. A limited action remedial alternative based on technical impracticability is proposed for this site. A drive point profiler was used to obtain 40 discrete interval groundwater samples from a total of five locations in nine days of field work. The drive point profiler enabled sampling of fine-grained, low permeability units in which monitor wells would not usually be installed. Samples were analyzed in a mobile laboratory for volatile organic compounds: trichloroethene, 1,2-dichloroethene, and vinyl chloride. The investigation produced useful information about the highly variable distribution of these compounds in the overburden units.

A new piston sampler allows the collection of high-quality core samples from sand, silt or clay, up to depths of 18 meters. The sampler is operated by a one- or two-person crew without a drilling rig. The sampler and ancillary equipment fit easily into a half-ton truck, making this a highly portable sampling system. Other advantages include minimal mechanical disturbance and precisely known sample depth. Casing is not required to maintain an open corehole below the water table and drilling fluid is not used in the corehole, so the solids and pore water of the sample should not be contaminated by foreign fluids. High-quality samples for physical, geochemical, and microbiological characterization of the subsurface are easily obtained with this new device.