SILVER CITY, NM
On this page:
- What Is Being Done to Clean Up the Site?
- What Is the Current Site Status?
- EPA’s Involvement at the Site
On related pages:
Cleveland Mill is located in southwestern New Mexico, approximately 5.5 miles north of Silver City, New Mexico. The Site was a former mine and milling operation during the mining boom of the 1900's (gold, silver, copper mining). The Site includes 18 acres with 4 acres in mountainous terrain, and about 14 acres that extend down to a drainage area (intermittent tributary creek) and into the streambed of Little Walnut Creek.
Mining and milling operations, including waste disposal activities left significant levels of tailings at levels that threatened the tirbutary creek and headwaters of Little Walnut Creek. Heavy metal contaminants included aresenic, beryllium, cadmium, lead, and zinc.
The tributary creek located immediately below the former mill contained acidic water and drainage. Concern regarding the stream quality was brought to the attention of the State of New Mexico and EPA by concerned citizens. EPA and the state of New Mexico began an investigation and in March of 1989, the Site was later listed onto the National Priorities List (NPL).
The formal Supefund CERCLA investigation began once the Site was listed onto the NPL. Although the "toe" of a tailing pile contaminated the shallow aquifer with beryllium and cadmium, groundwater sampling data did not indicate exceedances to heavy metals. However, EPA was concerned with sulfate detections observed in two residential wells. No site contaminants were orbserved in private wells or in monitoring wells exceeding water quality standards other than the elevated sulfate detections. Sulfates can sometimes be an indication of decreasing water quality trends. As a precaution, EPA conducted a "removal action" to rid the tributary creek of the mine and milling material and tailings that continued to affect the surace water and potentially the groundwater from contamination. The on-site waste material and tailings were also creating observable acidic conditions along the creek and creek bed during heavy rainfall. After removal actions were completed and sufficiient data was collected to demonstrate stability, the Site was taken off the National Priorities List in 2001.
What Is Being Done to Clean Up the Site?
The Site is maintained by the potentially responsible parties (PRPs) with State and Federal oversight.
The remedy addressed the tailings from the former mine and milling operation in order to protect Little Walnut Creek, its nearby tributary, and the surrounding surface or groundwater from the potential threat, particularly to residential wells.
What Is the Current Site Status?
The Site is no longer on the National Priority List. The Site however, continues to undergo annual operation and maintenance. The Site’s long-term remedy, selected in 1993, included excavation, treatment and disposal of waste material, and groundwater monitoring. However, a time-critical removal action, or short-term cleanup, became necessary in order to address the immediate threats to the creek and down-gradient water quality. The time-critical removal was conducted because unusually heavy summer rains created an unforseen threat to the creek and water quality by washing the mine tailings into the creek and dropping the acidity of the surface water to critically low levels. Removal actions in 1998 included excavation, treatment and disposal of waste material into an on-site disposal repository. EPA updated the long-term remedy in 1999 to state that the site required no further actions except continued groundwater and surface water monitoring and institutional controls. EPA took the site off the NPL in 2001.
EPA’s Involvement at the Site
The site is located in a developing residential area next to Gila National Forest and private lands. Downstream residences are near Little Walnut Creek, and a great majority rely on private wells for potable water and agricultural uses. The nearest residence is located about 1,000 feet west of the site. The population within a three-mile radius of the site is about 1,200 based on the last census. The present and anticipated future land uses for the site and surrounding areas are residential, recreational and agricultural with limited grazing of cattle.