NPL Partial Site Deletion NarrativeCalifornia Gulch
On July 23, 2001, EPA deleted Operable Unit 2 (Malta Gulch Tailing Impoundments and Lower Malta Gulch Fluvial Tailing (OU2) of the California Gulch site from the National Priorities List (NPL).
The California Gulch site is located in Lake County, Colorado approximately 100 miles southwest of Denver. Located in a highly mineralized area of the Colorado Rocky Mountains, the California Gulch site covers 16.5 square miles of the watershed that drains along the California Gulch to the Arkansas River. According to the 1994 Consent Decree, the site was divided into 12 Operable Units in order to expedite clean-up. Operable Unit 2 (OU2) includes the Lower Malta Gulch Fluvial Tailing, Malta Gulch Tailing Impoundments, Malta Tailing Impoundment, and the Leadville Corporation Mill.
The fluvial tailings in Lower Malta Gulch lie directly downstream of the Malta Gulch Tailing Impoundments. Approximately 800,000 tons of tailings were deposited in low profile berms that were unsuccessful in completely containing the tailings. A time critical removal action for Lower Malta Gulch Fluvial Tailing was performed during the 1995 and 1996 construction seasons. Revegetation work in Malta Gulch was performed in 1996. Subsequent monitoring in 1997 and 1998 have verified that the revegetation was successful and no long-term monitoring is required.
The Malta Gulch Tailing Impoundments (MGTI) are located at the upper end of Malta Gulch about two miles west of the City of Leadville. Results from a 1993 Engineering Evaluation/Cost Analysis (EE/CA) identified the presence of lead in the range of 800 to 57,600 parts per million (ppm). Based on these findings, EPA conducted a non-time critical removal to consolidate, grade, cap, and revegetate the MGTI.
The Malta Tailing Impoundment (MTI) is located 1.5 miles west of Leadville and 0.6 miles north of California Gulch. The MTI consists of three small impoundments, surrounded by berms. These impoundments contained tailings and pyritic material that presented a risk to human health and the environment since they are a source of acid mine drainage. In the fall of 1996, EPA conducted a removal action to consolidate the acid-generating materials, neutralize the acidic leachate, and grade, cap, and revegetate the MTI. Confirmation samples showed the revegetated soil surface of the impoundment to be below the 6,700 ppm total lead commercial/industrial site standard.
Long-term monitoring of the MGTI and MTI will be conducted in order to ensure that: (1) the cover material and vegetation remain effective, (2) future zoning is consistent with the remedy, and (3) groundwater is not utilized as a source of drinking water.
The Leadville Corporation Mill is located at the southern boundary of the MGTI. In 1998, the EPA conducted an emergency removal action to remove 36 55-gallon drums containing acids, bases and flammable liquids from the Leadville Corporation Mill. Complete removal of the drums was accomplished and no further monitoring is necessary for this portion of OU2.
The EPA and the State of Colorado have determined that all appropriate CERCLA response actions have been completed and OU2 poses no significant threat to human health or the environment. Therefore, EPA is deleting OU2 of the California Gulch Superfund Site from the NPL.