The former Twin Cities Army Ammunition Plant (TCAAP) is a 4-square mile site located in New Brighton/Arden Hills, Minnesota. The extent of the contamination covers a 25-square mile area. Land use in the area consists of residential, commercial, and industrial with on-site wetlands and woodlands surrounding Rice Creek watershed. From 1941 to 1981, the site was used to manufacture, store, and test small arms ammunition and related equipment. Waste materials such as VOCs, heavy metals, corrosive materials, and explosives were disposed at 14 source areas, several of the source areas impacted by test firing activities were targeted for remediation to remove metals and reduce the toxicity characteristics concentrations of the soil. 

The remedial objective for this work included on-site stabilization of contaminated soil to below the Toxicity Characteristics (TC) criteria for lead and antimony and off-site disposal. 

Phytoremediation and lead-extraction processes were implemented in earlier remediation phases of the TCAAP project. In 1998 EnviroBlend® was selected in a competitive bid process to stabilize additional soil. Total lead concentrations in the soil were between 113,000 and 330,000 mg/kg. Stabilization with EnviroBlend achieved results below the TC criteria of 5.0 mg/L for lead in the Toxicity Characteristic Leaching Procedure (TCLP) test. 

Contaminated soil at the TCAAP site was characterized, excavated, and stockpiled. A coarse granular EnviroBlend was thoroughly mixed in the stockpiles using conventional construction equipment at a recommended dosage rate of 3%. The EnviroBlend stabilization process does not require the use of water or a curing period. The treated material was then analyzed using the TCLP test. All stabilized material passed the TC criteria and was disposed in a Subtitle D landfill. Ethylene diamine tetra acetic (EDTA) acid was found in soil at a portion of the site, potentially left over from former lead-extraction processes implemented at the site. EDTA complexes lead and other heavy metals and increases their leachability. Through a quick-turnaround treatability study in RMT’s applied chemistry laboratory, RMT demonstrated treatment effectiveness using EnviroBlend on a representative sample of soil contaminated with lead and EDTA. 

EnviroBlend was used for the stabilization of the 47,000 tons of soil. The total project cost was $777,000 for soil stabilization assistance, including treatability studies, technical assistance, pilot studies, and reagent supply. 

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