1261492 -R8 SDMS 

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

REGION 8 

1595 Wynkoop Street 

Mailcode: EPR-SA 

DENVER, CO 80202-1129 

Phone (800) 227-8917 

http://www.epa.gov/region08 

Ref: 8EPR-SR May 16, 2013 

MEMORANDUM 

SUBJECT: Minor Modification of the Selected Remedy 

California Gulch Superfund Site 

American Smelting and Refining Company (ASARCO) Smelters/Slag/Mill Sites 

Operable Unit 5 

Lake County, CqTotjado 

FROM: Linda Kiefer 

Project Manager 

TO: California Gulch Superfund Site File 

PURPOSE 

The purpose of this memorandum is to document the Environmental Protection Agency's (EPA's) 

justification for a minor modification of the remedies selected for Operable Unit 5, the California 

Gulch Superfund Site (the Site). EPA issued two RODs for OU5: the ROD for the AV/CZL sites 

on OU5 was issued on September 29, 2000, and the ROD for the EGWA sites on OU5 was 

issued on October 31, 2000. This modification applies to both RODs. 

The modification described herein is considered minor because it has non-significant or minor 

impact on the overall scope, performance, or cost of the selected remedy. 

BACKGROUND 

Both the September 29, 2000 and the October 31, 2000 ROD discuss the use of an overlay 

district which would provide a screening process to identify properties where special precautions 

or requirements may be needed. The overlay district was ratified by the Lake County 

Commissioner in November 2004 and then repealed in April 2005. 

The contaminants of concern (COCs) are arsenic, cadmium, copper, lead, and zinc. 

MODIFICATION OF THE SELECTED REMEDY 

EPA and CDPHE have determined that institutional controls are needed for waste left in place to 

assure that contaminated soils above the action levels for two of the contaminants of concern 
(COCs), lead and arsenic, for residential or commercial properties which ever is the case, and 

fine slag are removed or covered before residential or commercial uses are made of the property, . 

to ensure proper maintenance of any cover and to protect human health and the environment. 

The objectives of the institutional controls are as follows: 

1. Reduce or control human exposure to contaminants of concern, 

and 

2. Maintain the integrity of and prevent disturbances of the engineered features or 

structures of the current or future remedies. 

Lake County passed an ordinance, which was recorded by the County Clerk on April 15, 2013, 

establishing institutional controls for OU5. Under this ordinance, for areas where in OU5 with 

engineered remedies, the County will not issue a permit for any activity on property that contains 

a designated engineered remedy unless the permit applicant has secured approval for those 

activities from the CDPHE. For all other portions of OU5 not designated as part of an engineered 

remedy, the ordinance provides that any excavation or other earth removal activity that exceeds 

10 cubic yards requires CDPHE approval for such activity as a condition precedent to the County 

granting a permit. Finally, the ordinance provides that all permit applicants shall be provided 

with irrforrriation regarding best management practices regarding potentially contaminated soils 

and the applicant must certify they have received and reviewed this information before a permit 

will be issued. 

BASIS FOR THE DETERMINATION THAT MODIFICATION IS MINOR 

This modification is considered to be non-significant or minor based on the following: 

• Scope: This modification does not change the containment technology, the physical area 

of the response, remediation goals to be achieved, and the type and volume of wastes to 

be addressed. 

• Performance: This modification does not change the performance of the existing remedy. 

• Cost: The costs of establishing and implementing the ordinance versus the overlay district 

are expected to be similar. 

cc: Craig Gander, CDPHE 

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