SITE INFORMATION AND CORRESPONDENCE_FILE 1

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JUL-02-99 15:27 frow:URS GREINER SF 4153991904 • T-934 P 06/07 Job-959 Rapid,from page 9 ^>1 • concentration was 20,100 mg/kg. — 'j"' Cleanup technologies considered �( for the site included air,steam and i ;S biosparging via horizontal wells, in-situ and ex-situ thermal and biological treatment,and off-site incineration and disposal.Most of these were not technically viable in clay soils or were prohibitively expensive.In a joint venture by GCI,QST Environmental Inc.and w, the US.Army Coups of Engineers, a performance demonstration of in- situ chemical oxidation occurred in December 1996. The demonstration lasted 18 days. About 30.000 L of 50 percent hydrogen peroxide plus catalyst solution were injected via 20 injectors ranging in depth from 13 to 18.3 in below grade in a 232 m? portion of the most contaminated area Post-injection sampling Indicated an average 87 percent reduction(with a range of 47 percent to 100 percent)in volatile organic compounds in the treated Injector and mixing head used during the performance area after the demonstration. demonstration at the Anniston Army Depot.Reagents are Injected Based on these results,a full-scale under pressure to achieve a large radius of influence around the remediation program was initiated injector. and is in progress.About 250 injectors were installed to the amount and nature of the than for dig-and-haul or encompass the plume.The contaminant,and the hydraulic incineration technologies.One program is scheduled to proceed conductivity of the formation. important advantage of in-situ over five months and deliver about These factors determine the chemical oxidation,which also 361,000 L of 50 percent hydrogen number of injectors,amount of affects cost effectiveness,is the peroxide solution.To date,after hydrogen peroxide and other relative speed of the remediation injection of about 218,000 L of 50 reagents,and time necessary to program.Injection programs percent hydrogen peroxide over deliver the reagents to the typically range from weeks for three and a half months,analyses of subsurface,which cumulatively small sites of tens of square meters 30 soil samples indicate determine the final cost. to months for large sites in hectares. trichloroethene destruction ranging Unit costs are less than$50 per In general,chemical oxidation is from 65 percent to more than 99 kilogram of contaminant oxidized not the most cost-efficient approach percent.See figure 4,page 11.Costs for sites with high levels of for treatment of large,low- for the in-situ chemical oxidation DNAPL%and large size.At the concentration plumes.Exceptions treatment are an estimated$1.4 opposite end of the spectrum,unit include situations in which time is million,excluding consultant coats can range as high as several an issue or other remediation oversight and pre-and post- hundred dollars per kilogram of technologies are not feasible.The injection characterization. contaminant for relatively small duration of a chemical oxidation �; sites of tens of square meters with treatment is often on the order of Cut OII1414 relatively low contamination(µg/L weeks,in contrast to other Unit costs for in-situ chemical levels dissolved in groundwater). technologies for which cleanup oxidation have a considerable These costs are generally higher duration ranges from months to range.Controlling factors include than for bioremediation,pump- years. the volume and distribution of and-treat,or other passive One of the most cost-effective contaminated soil or groundwater, technologies,but significantly less applications for in-situ chemical • i 10 August/September 1998 Soil A Groundwater Cleanup