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Phytoremediation at Twin Cities Army Ammunition Plant, Minneapolis-St. Paul, Minnesota

Site Name:

Twin Cities Army Ammunition Plant


Minneapolis-St. Paul, Minnesota

Period of

Spring and Summer 1998


Field demonstration


Ms. Darlene F. Bader
U.S. Army Environmental Center
5179 Hoadley Road, Bldg E4430
Aberdeen Proving Ground, MD 21010-5401
Telephone: (410) 436-6861
E- mail:

- Demonstration used 0.2-acre plots at Site C and Site 129-3
- Sites were prepared by clearing, fencing, plowing, and installing an irrigation system
- Two crops were grown on each site; first corn and second white mustard
- Amendments (acetic acid and EDTA) were added to the soil to aid in the solubilization and uptake of lead
- Each crop was harvested and smelted

Cleanup Authority:
Not identified

Site Contact:
Not identified
Regulatory Contact:
Not Identified

Heavy metals
- Site C: antimony, arsenic, beryllium, lead, and thallium; average of 2,610 ppm lead in surface soil
- Site 129-3: antimony, barium, chromium, and lead; average of 358 ppm lead in surface soil

Waste Source:
Burn areas, pits used for wastewater disposal

Type/Quantity of Media Treated:
- Climate conditions included an average annual precipitation rate of 28.6 inches and an average annual temperature of 49.6øF; the location also can have early/late frosts
- Soil type at Site C is peat, underlain by fine sand and sandy clay; at Site 129-3, fine- to medium-grained sand
- Depth to water table at Site C is 2 to 6 ft bgs; at Site 129-3, 140 to 200 ft bgs

Purpose/Significance of Application:
Phytoremediation of heavy metals in soil in a northern climate

Regulatory Requirements/Cleanup Goals:
- Determine if phytoextraction is a technically and economically feasible means of reducing lead contamination from near-surface soils; specific cleanup levels not identified

- Results from the first year's demonstration showed less than anticipated biomass yields and lead uptake in the harvested plant material
- Corn yielded 2.1 to 3.6 tons of corn stover per acre, compared to the anticipated yield of 6.0 tons per acre ; poor yields were attributed to agronomically low producing soils at the site and the presence of other soil contaminants
- Lead concentrations in harvested corn averaged 0.65% and 0.13% dry weight for Sites C and 129-3, compared with the 0.85% removal obtained during a prior greenhouse study
- White mustard yielded 1.9 to 2.1 tons of white mustard per acre of land; on a per plot basis, the total yields for Site C were half of this value since the white mustard grew in only about 50% of the plot area
- In the areas where plants grew, the yields were comparable to the expected yield of 2 tons per acre of mustard
- Lead concentrations in harvested white mustard averaged 0.083% and 0.034% dry weight for Sites C and 129-3, compared with the 1.5% obtained during greenhouse studies

Cost Factors:
- USAEC developed a preliminary cost estimate for a typical full-scale phytoextraction project in a northern U.S. location, with two crops grown per year (one corn and one white mustard), sub-optimal soil conditions for plant growth, soil lead levels of about 2,500 ppm, and five years of remediation required to meet the regulatory standard
- The projected cost for full-scale phytoextraction was $30.34 per cubic yard of soil per year, or about $153 per cubic yard of soil over the life of the project

The Twin Cities Army Ammunition Plant (TCAAP) is a 2,370-acre facility located in Arden Hills, Minnesota, approximately 10 miles north of Minneapolis-St. Paul, Minnesota. The TCAAP was used for the production and storage of small arms ammunition, related materials, fuzes, and artillery shell materials. A phytoremediation demonstration was conducted at areas within Sites C and 129-3 at the TCAAP. Site C was used for burning production materials and decontamination equipment. Site 129-3 contained pits that were believed to have contained contaminated wastewater from a lead styphanate production facility. The project is a two-year field demonstration executed under a partnering agreement among the U.S. Army Environmental Center (USAEC), Tennessee Valley Authority (TVA), TCAAP, and the U.S. Army's Industrial Operations Command (IOC).

During the first year, phytoremediation was conducted at thee sites using corn and white mustard, and results were less than anticipated. Changes planned for 1999 to improve performance included use of alternate mustard varieties; use of higher fertilizer rates to encourage greater biomass; varying the irrigation scheme to encourage rooting and growth; alternate amendment delivery systems; deep tilling; and alternate EDTA degradation methods