NPL Partial Site Deletion NarrativeCalifornia Gulch
On April 22, 2002, EPA deleted subunits A and B of the residential populated areas, residential waste rock piles, and the parks and playgrounds within Operable Unit 9 (OU9) of the California Gulch Superfund site, Lake County, Colorado, 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.
OU9 of the California Gulch site includes the subunits A and B of the residential populated areas, the residential waste rock piles, and the parks and playgrounds. A site-wide Phase I Remedial Investigation (RI) which primarily addressed surface and groundwater contamination was issued in January 1987. The Phase I RI was followed by a number of additional site-wide studies. The specific OU9 studies that were conducted included the Soil-Lead in Residential Populated Areas RI, Parks and Playgrounds Engineering Evaluation and Cost Analysis (EE/CA), Mine Waste EE/CA, and the Final Residential Soil Feasability Study (FS). The studies have determined lead to be the primary contaminant of concern in OU9. The RI, completed in May of 1994, identified soils as the primary exposure pathway to the residential population at the site. The Final Residential Soil FS, completed in November of 1998, evaluated the residential soils of properties, yards and open space areas where lead levels exceeded the trigger level of 3,500 ppm and presented seven remedial alternatives.
The residential populated areas of the California Gulch site are comprised of the City of Leadville, Stringtown, and outlying areas zoned for residential use. Subunits A and B are located within the outlying areas zoned for residential use within OU9. The RI and Terrestrial Risk Assessment have shown that taking remedial measures is not appropriate for subunits A and B.
A Mine Waste EE/CA was prepared in December 1995 to identify removal action alternatives for the mine waste piles within OU9. Fourteen residential waste rock piles with lead concentrations greater than 3,500 ppm were removed and placed at end use locations. Residential waste rock piles which fell below action trigger levels were left in place. In addition, eight suspected mine shafts were closed using a monolithic concrete plug. Confirmation sampling showed that removal had successfully lowered lead levels to below site clean up levels of 3,500 ppm. Thus, no long term monitoring is required. This removal action is consistent with the performance of the final remedial action for OU9 and is considered as the final remedy for waste mine piles within OU9.
A Parks and Playgrounds EE/CA was prepared in November of 1994. Based on the finding that soils at all parks and playgrounds were below the trigger level of 3,500 ppm lead, EPA approved no further action for the areas addressed by the work plan. Subsequent to the Parks and Playgrounds EE/CA, one additional playground area was identified in Leadville. A Soil Remediation Site Plan was developed under the direction of the Kids First Program, pursuant to the Record of Decision for Residential Soils. Testing revealed that soils exceeded the trigger level of 3,500 ppm lead, and remedial actions involved the removal of 231 cubic yards of soil. Existing playground equipment was also removed. The excavated area was then filled with top soil and revegetated. Soil confirmation samples indicated that the soil lead concentrations were below the established action levels of 3,500 ppm.
Based on the successful completion of the removal action and the remedial action, there are no further response actions planned for subunits A and B, residential waste rock piles, and the parks and playground within OU9. Because this decision results in hazardous substances remaining on site, above health-based levels, five-year reviews of the previous response actions will be required pursuant to the NCP. These reviews will be conducted in conjunction with site-wide five-year reviews. The Second Five Year Review Report for California Gulch, signed in September of 2001, concluded that the remedy for OU9 currently protects human health and the environment. The next five-year review at the California Gulch site is scheduled for completion in September of 2006.
The EPA, with concurrence of the State of Colorado, has determined that all appropriate responses under CERCLA have been completed, and that no further response actions, under CERCLA, other than five-year reviews, are necessary. Therefore, EPA is deleting subunits A and B, residential waste rock piles, and the parks and playgrounds within OU9 from the NPL.