Cement production at this site north of Mason City, Iowa ran from 1908 to 2009. From 1969 to 1985, the company disposed of roughly 2 million tons of cement kiln dust in a former limestone quarry called the West Quarry. That dust contains calcium oxide, which reacted with water to raise pH levels in nearby groundwater and surface water to harmful levels. The site was added to EPA's National Priorities List in 1990.
EPA identified 13 contaminants of concern, all found in groundwater and surface water. They include antimony, arsenic, cadmium, cement kiln dust, chromium compounds, copper, lead, mercury, nickel, phenol, and zinc. High pH in soil also posed risks from direct contact, and a fish kill occurred in Calmus Creek in 1986. Chromium, lead, sodium, sulfate, and other heavy metals were detected in private drinking water wells.
Cleanup construction was completed in December 1993. Work included capping the quarry with clay, installing seven groundwater extraction wells, and building a water treatment system that lowers pH before discharging water to Calmus Creek. The site was deleted from the National Priorities List in August 1995. Groundwater pumping and treatment continue to operate and prevent contamination from spreading. Human exposure to contaminated groundwater and direct contact with contaminated soil are no longer concerns.
The most recent Five-Year Review, completed in June 2022, confirmed the remedy remains protective of human health and the environment. One issue was noted: moderate erosion north of the retention pond that earlier repairs did not permanently fix. A workplan to address the erosion was submitted in December 2024, and repairs are scheduled to begin in late spring or early summer 2025. The next five-year review is estimated for June through August 2027.
Institutional controls remain in place. An environmental covenant recorded in October 2016 prohibits drinking water wells and irrigation wells for food and feed crops. Residential use requires written EPA approval, and any excavation of the soil cap also needs advance written approval from EPA. Community members with questions can contact EPA's Community Involvement Coordinator, Shaylee Borcsani, or Remedial Project Manager, Victoria Frank. The Iowa Department of Natural Resources contact is Matthew Graesch.
