Monitor-wells investigations

Investigators must exercise professional judgment when interpreting analytical results from monitoring wells. In real-world situations, many other factors are involved that may interfere with the ideal. For example, the soil may contain line particles (clays or free organic carbon) that have an affinity for a particular component or certain microfluora that biodegrade some molecules more easily than others. 

Preliminary estimates of LNAPL made during the investigative phases of a project are usually based on the results of short-term pumping tests, approximations of actual LNAPL thickness based on gauging data generated from monitoring wells, and other approximate data. The numerical estimates based on this short-term information are often adequate to define the physical parameters sufficiently for prelim-... 

For over a decade, LNAPL occurrence has been investigated beneath an active refinery site in southern California. Numerous monitoring wells along with LNAPL samples have been used to evaluate the extent and character of LNAPL occurrence. LNAPL was found to occur as five pools. The main pools each consist of individual accumulations of distinct product types occurring under both perched and water table conditions. Two different recovery and mitigation strategies have been utilized. In relatively high permeability zones, a system of two-pump recovery wells was used to recover fluids recovered water is reinjected without treatment. In relatively low permeability zones, a system of one-pump recovery wells was used. In the latter case, recovered water is treated prior to disposal. 

CASE 4 - Determination of areas characterized by salt water intrusion (integrated evaluation of geophysical data and electrical conductivity data from direct investigations in monitoring wells)... 

The percent wastewater was calculated by the investigators from the chlorine concentration in the monitoring well (5800 mg/1) and the initial chlorine concentration in the lower limestone aquifer (7900 mg/1) ... 

New York City, which drew some of its water supply from a point three and a half miles to the south, installed seven shallow test wells near Liberty Aircraft in 1945 and initially found no contamination. When the war ended, further investigations began, with dozens of new monitoring wells installed. In 1948, chromium was detected in three of the city test wells near Liberty, and a plume of contamination was traced for a mile from the plant. At Grumman, chromium had been found in public supply wells more than 100 feet deep. By 1949, all of Long Island s aircraft plants had installed treatment systems to remove chromium from their wastewater.31... 

Several methods are available for the drilling and installation of monitor wells. The advantages and disadvantages relating to ease of construction, character of formations penetrated, well diameter and depth, risks of contamination, and intended use of the well have been reported by several investigators ( 5, 6, 7). All field personnel should be thoroughly familiar with well specifications, quality assurance/quality control procedures, and safety plans and requirements prior to installation of monitor wells. 

No testing was done as part of this investigation of interceptor and monitoring wells drilled on-site but a number of tests were made on Thornton Spring water samples 0.9 km below the plant. 

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