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Based on aquifer performance tests, 13 out of 15 wells situated at the Mixed Waste Disposal (MWD) area located at the Savannah River site. South Carolina, exhibited high skin factors and low well efficiencies indicative of severely damaged wells. The use of damaged wells in aquifer testing can lead to inaccurate determinations of aquifer properties, and such wells are unusable in future remediation programs. Moreover, damaged wells can go dry during purging, thus compromising sample collection. Pump tests, chemical analyses, and biological investigations revealed that the poor well performance at MWD was attributable to calcite precipitation on the well screen and drilling mud in the filter pack. The calcite problem resulted from improper well installation, and the drilling mud in the filter pack was due to inadequate well development. Experimental rehabilitation procedures employed on two wells, MWD 5A and 1A, included acidification, swabbing, introduction of surfactants, and surging. Treatment of the wells substantially improved well yields, skin factors, and well efficiencies. Moreover, well rehabilitation was determined to be a reasonable alternative to drilling new wells at the MWD wellfield.

A: NAPL, nonaqueous phase liquid; VOC, volatile organic contaminant.S S : V Z M Steam fl ooding is used for removal of vola le organic contaminants (VOCs) from concentrated source zones. The applica on of steam fl ooding to shallow vadose zone sites can be problema c if the steam or contaminants vent to the ground surface. Cold air injec on holds promise as a technique for controlling the ver cal movement of the injected steam. A series of two-dimensional numerical simula ons using a radially symmetric grid show the sensi vity of this process to geological and opera onal parameters. Air control of ver cal steam movement appears to be a useful technique, using approximately equal air and steam volumetric fl ow rates. Air injec on is shown to be more eff ec ve than a low-permeability cap at the ground surface for keeping high temperatures away from the surface. The most eff ec ve design appears to be a combina on of a low-permeability surface cap and air injec on above the steam injector. The cap mainly serves to direct the air fl ow, preven ng it from exi ng at the ground surface near the air injec on point.

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