Monitor-wells sampling

Figure 8. Anion exchange chromatogram with UV detection (210 nm) of a lyophilized ground water monitoring well sample taken from the Casmalia hazardous waste site.

A uniform and constant Darcy velocity of 15 myear-1 and effective porosity of 0.3 were used along the entire cross-section. The tailings fluid has relatively high chloride concentrations (0.016 mol L 1) compared with the background water has only 0.0007 molL-1. It is widely believed that Cl- acts as a conservative solute in most aquifer systems, and thus its distribution can be used to retrieve dispersivity for the aquifer. By trial and error, a longitudinal dispersivity between 10 to 15 m appears to fit the concentration differences best in monitor wells sampled in September, 1994. It... 

It is often important to quantify the contamination of pore fluid in the unsaturated soil 2one, where monitoring wells are ineffective. In this region, suction cup lysimeters are useful (7). These samplers consist of a porous cup, typically ceramic, having two access tubes which are usually Teflon. One access tube provides a pressure-vacuum, the other discharges the sampled fluid to the surface. The porous cup, typically between 2 and 5 cm in diameter, is attached to a PVC sample accumulation chamber. 

Locational considerations include both surficial location and screened interval, ie, the sampling depth. The surficial location is selected based on whether the sample is to represent background quaUty or quaUty at the location of contamination, or potential leak location. In selecting the surficial location, the groundwater flow parameters, velocity and direction, are assumed to be known from other monitoring wells or borings already completed. 

Detailed sampling can include, but is not limited to, the installation of monitoring well networks. After the wells have been installed, aquifer tests are typically performed. Once the aquifer tests are performed and the aquifer characteristics are determined, time series sampling for a given contaminant, or a surrogate, is undertaken. The combined results of these efforts provide the basis for development of a treatment strategy. Modeling can be used as part of this effort to help determine the best technical and most cost-effective techniques to be used at a site. 

Monitoring Well Purging and Sampling Form MW and MW Event ... 

Figure 2 Example of a monitoring well purging and sampling form...

Suction lysimeters are required for some field-scale groundwater monitoring studies to monitor the transport of compounds of interest through the unsaturated zone. Unlike monitoring wells or water supply wells that sample water from the saturated zone, suction lysimeters sample water from the unsaturated zone. This section provides a summary of the installation and sampling procedures for pressure-vacuum suction lysimeters. A detailed discussion of unsaturated zone sampling devices is available elsewhere. 

Elkan and Horvath170 performed a microbiological analysis of samples taken from the north and south deep monitoring wells in December 1974, about 6 months after the dilute waste front had reached the south well. Both denitrifying and methanogenic bacteria were observed. The lower numbers and species diversity of organisms observed in the south monitoring well compared with those in the north well indicated suppression of microbial activity by the dilute wastes. 

Waste injection began in June 1975, and waste was first detected in the downgradient southwest deep monitoring well about 260 days later. To analyze the waste s physical and chemical properties after injection, the primary injection well was allowed to backflow into a holding pond for 5 days in November 1977. This waste was sampled periodically (and reinjected when the test was completed). About 4 years after injection began dilute waste arrived at the standby injection well 476 m (1560 ft) south of the primary well. 

A common laboratory device is a batch reactor, a nonflow type of reactor. As such, it is a closed vessel, and may be rigid (i.e., of constant volume) as well. Sample-taking or continuous monitoring may be used an alternative to the former is to divide the reacting system into several portions (aliquots), and then to analyze the aliquots at different times. Regardless of which of these sampling methods is used, the rate is determined indirectly from the property measured as a function of time. In Chapter 3, various ways of converting these direct measurements of a property into measures of rate are discussed in connection with the development of the rate law. 

Physical and chemical monitoring is carried out through a U-tube downhole installation (Freifeld et al. 2005) that allows the collection of high quality liquid and gas samples from targeted depths. The multi-level U-tube assembly is completed in the Waarre C unit approximately 300 m distant and updip from the injector well (CRC-1). The Naylor-1 monitoring well is perforated from 2028.3 - 2032.2 m RT and 2039 - 2055 m RT. The U-tube assembly is constructed to sample from U1 at 2027 m RT (gas cap), U2 2040 m RT and U3 2045 m RT both initially below the gas-water contact. 

Monitoring wells were installed to a depth of 3-4 m into soft tailings at sites 1 and 2. The wells are constructed of 1.5 inch-OD PVC pipe with the lower 1.2 m perforated for collection of ground water. Water was sampled using a LDPE tubing- foot valve assembly. Ground water and surface waters were sampled monthly from August to November 2008. Temperature, pH, and conductivity were measured in the field and... 

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