Piezometers

Specifications for Piezometer Taps The size of a static opening should be small compared with the diameter of the pipe and yet large compared with the scale of surface irregularities. For rehable results, it is essential that (1) the surface in which the hole is made be substantially smooth and parallel to the flow for some distance on either side of the opening, and (2) the opening be flush with the surface and possess no burr or other irregularity around its edge. 

Comparison of water levels in observation wells, piezometers, lakes and streams... 

Piezometer tube An open-ended calibrated glass or plastic tube that measures the pressure in a pipe or vessel full of a fluid. 

When the static pressure in a moving fluid is to be determined, the measuring surface must be parallel to the direction of flow so that no kinetic energy is converted into pressure energy at the surface. If the fluid is flowing in a circular pipe the measuring surface must be perpendicular to the radial direction at any point. The pressure connection, which is known as a piezometer tube, should terminate flush with the wall of the pipe so that the flow is not disturbed the pressure is then measured near the walls where the velocity is a minimum and the reading would be subject only to a small error if the surface were not quite parallel to the direction of flow. A piezometer tube of narrow diameter is used for accurate measurements. 

For the flow not to be appreciably disturbed, the diameter of the instrument must not exceed about one-fiftieth of the diameter of the pipe the standard instrument (diameter 7.94 mm) should therefore not be used in pipes of less than 0.4 m diameter. An accurate measurement of the impact pressure can be obtained using a tube of very small diameter with its open end at right angles to the direction of flow hypodermic tubing is convenient for this purpose. The static pressure is measured using a single piezometer tube or a piezometer ring upstream at a distance equal approximately to the diameter of the pipe measurement should be made at least 50 diameters from any bend or obstruction. 

Soil samples were collected along a traverse over the Honerat kimberlite and extended off the kimberlite approximately 75 m SE and 225 m NW from the pipe s centre (Fig. 1). Although it is common practice to collect samples from upper B-horizon soil (Levinson 1980 Bajc 1998 Mann et al. 2005) our samples were collected from C-horizon soil because GAGI samplers were placed at a depth of 60 cm (well below the B horizon). Within 8 hours of sampling, a portion of each soil sample was mixed with Milli-Q water (1 1) to create a slurry. The values of pH and oxidation-reduction potential (ORP) were determined in each slurry. Ammonia acetate leach of the soil samples were performed at Acme Analytical Laboratories, Vancouver, where 20 ml of ammonium acetate was mixed with 1 g soil sample and elements were determined by inductively coupled plasma-mass spectrometry. The GAGI samplers installed at Unknown were placed in piezometers and submerged in water at a depth of approximately 1 m below ground surface. 

Fieldwork was conducted at Attawapiskat kimberlites (Yankee, Zulu, Alpha-1, Bravo-1, and X-ray), and at the Control location August 14-23, 2007 and October 14-18, 2007. Shallow piezometers were used to collect peat groundwater. At the Yankee and Zulu kimberlites piezometers were installed along transects between 25 to 50 m apart. Between 3 and 5 piezometers were installed at Alpha-1, Bravo-1, and X-ray. Piezometers were typically pushed into the peat 1.1 m with a loosely fitting plastic champagne cork at the end to prevent peat entering the pipe while it was... 

Waters collected from piezometers and monitoring wells were analyzed for metals using an ICP-AES and ICP-MS at the Ontario Geological Survey. Anion contents were also determined at the Ontario Geological Survey using an ion chromatograph. 

Samples of groundwater were obtained from piezometers installed at various locations throughout the tailings. Groundwater was retrieved using a baler. Pore water was squeezed from samples of solid tailings. All water samples were analysed for cations, anions, Eh and pH. 

The piezometers were also used to estimate the hydraulic conductivities of the tailings. The Seep/W software package, was used to model the flow from the tailings into the drainage trenches. 

Two hydraulic head gradients determined from wells or piezometers are shown in Figure 3.15. Piezometers are basically pipes or wells put in the ground which are... 

FIGURE 12.18 Corrected water table piezometer surface contour map showing regional hydrogeologic gradient toward the southwest. Note the impact of recovery systems within their area of influence or capture zones. (After Testa et al., 1989.)... 

Piezometer Method. To measure the compressibility of liquids near 1 atm we have developed a piezometer system (87). 

A sketch of this system is shown in Figure 4. The piezometer,... 

C, is a cylindrical glass vessel with a volume of 450 cm. The piezometer contains the solution and 330 gms of Hg. The top of the piezometer is fitted with a Taper joint for filling. A precision bore capillary, E, (2mm in diameter) is fitted to the bottom of the piezometer. The piezometer is suspended (6) in a brass or stainless steel pressure vessel, H. A glass boiler tube, J, encloses the upper portion of the capillary. The pressure vessel is filled with ethylene glycol which serves as a thermal and pressure medium. The entire apparatus is submerged in a constant temperature bath controlled to 0.001 C. The temperature inside the pressure vessel is monitored with a Hewlett-Packard quartz crystal thermometer (to determine when thermal equilibrium is reached after compression and decompression). 

High Pressure PVT Properties. The earlier volumetric methods (113,114) consisted of a piezometer, similar to the one shown in Figure 6, which is contained in a pressure bomb. The... 

Local Static Pressure In a moving fluid, the local static pressure is equal to the pressure on a surface which moves with the fluid or to the normal pressure (for newtonian fluids) on a stationary surface which parallels the flow. The pressure on such a surface is measured by making a small hole perpendicular to the surface and connecting the opening to a pressure-sensing element (Fig. 10-8a). The hole is known as a piezometer opening or pressure tap. 

Undegraded biopolymer slurry material remaining after trench construction may initially interfere with operations. Possible siltation interferences can prevent collection of samples from piezometers. A rise in upgradient water levels can result in potential blockage of groundwater flow, suggesting that airflow should be pulsed to allow for contaminated water to flow through the system. 

Results of the test showed that trichloroethylene (TCE) and perchloroethylene (PCE) concentrations in the water declined by more than 90% to below 2 parts per billion (ppb). All of the wells showed significant decreases in contaminants in less than 1 month. In four of the five piezometers (specialized monitoring wells whose primary purpose is the measurement of hydraulic head), TCE and PCE concentrations declined from as high as 10,000 parts per million... 

Physical Approaches. Groundwater-exchange rates with lakes are traditionally estimated by careful measurements of hydraulic potentials within the groundwater system, followed by application of Darcy s law in the form of flow-net analysis or numerical modeling. However, these measurements can be time-consuming and costly, and can require monthly to weekly measurements at many piezometers to examine the three-dimensional nature of the hydraulic-potential field. In addition, characterization of the hydraulic conductivity of the aquifer is critical to physical approaches and typically leads to results with large uncertainties (I, 2). 

The purpose of this chapter is not to promote the replacement of traditional physically based methods of assessing groundwater-lake systems with isotopic methods, but rather to demonstrate the utility of isotopic techniques. Physically based methods can provide more detailed information on the spatial and temporal variability of a groundwater-lake system than isotopic approaches can provide. Regardless of the method chosen, however, an adequate number of piezometers is necessary to ensure that groundwater samples are collected from upgradient areas. 

---