Typical response to APP application

DAMES & MOORE

Arizona Department of Environmental Quality

February 8, 1995

Page 2

officials. With the continuing evolution of federal and state environmental regulations, CSC voluntarily began a program of upgrading their existing facilities at the Sierrita operation to reduce or eliminate, where possible, potential releases to the environment.

STRATEGY FOR SITE IMPROVEMENTS

As presented in the APP application, there are numerous potentially discharging facilities on the CSC site. Due to operational considerations, most of these facilities have been built in several geographically localized areas. As an example, the facilities in the Esperanza Wash all deal with PLS coming from the 4521 leach dump area, located immediately north of the Esperanza Wash facilities. These facilities include the leach dump, Headwall Nos. 3 and 4, SX Plant No.3, and Raffinate Pond No. 3.

If this were a new mining operation, it would be relatively simple to design and build control structures that are multi-functional and that incorporate liners, leak detection systems, stormwater controls, and operational controls. The facilities and control structures for a new mine would probably look very similar to a perceived optimal BADCT.

CSC is not a new operation, it is in operation now and intends to continue 24-hour per day, 7-day a week operation for at least the next 15 to 20 years. It is impractical to presume that CSC could. or should abandon all the existing facilities and build new multi-functional control structures that conform to a presumptive BADCT adopted from new facility standards. The only practicable method to achieve discharge control would be for CSC to maintain existing operations and conform to regulatory requirements contained within Arizona Revised Statutes (A.R.S.) 49-243 to improve the existing facilities.

An expected question on facility improvement could be stated as: why not automatically upgrade a facility to a new facility optimal standard, such as double lining all regulated surface impoundments? An answer to this question is: �practicable design and construction indicates that a consistent level of control be utilized throughout a process system. The following would be an example of consistent controls:

If the handling of a specific operational solution, say PLS or raffinate, is well controlled in a vessel or pipeline, then prudent design measures should be taken to maintain a consistent level of solution control within a system. That is, if all the operational solution is controlled in the pipeline, then there is no reason for subsequent components of the system to be any less effective. For an operational

DAMES & MOORE

Arizona Department of Environmental Quality

February 8, 1995

Page 3

basin in this theoretical system, say a raffinate [the part of a liquid remaining after its more soluble components have been extracted by a solvent] pond, practicable design would indicate the use of double liners with a leak detection system.

In an area where the operational solution is only reasonably controlled, say at the toe of the existing unlined leach dump, a consistent level of solution control would involve a cutoff trench to collect the solution and a single-lined basin to contain the collected PLS. There is no practicable, demonstrated method to assure that all of the PLS solution is collected at the primary cutoff. Following the same, if there is no certainty that all the solution is collected and there are additional down gradient controls, there is no practical reason to have more than a single liner to contain the collected solution. In this scenario, the use of a double-lined PLS collection basin constitutes an unnecessary redundancy.

Since some PLS is expected to get past a primary collection facility, CSC operational designs incorporate a systems redundancy to collect and control solutions that manage to bypass the primary facility. This is the essence of CSC's systems approach to control of operational solutions.

RATIONALE FOR EVALUATING GROUPED FACILITIES AS SYSTEMS

Since most of the original facilities pre-date the effective date of the APP statute, CSC has to maintain operations with a group of facilities that were designed and constructed principally for operational considerations and not environmental concerns. The operational facilities or defined discharging facilities that existed at the CSC site in August 1986 are still in existence today.

However, for most of the facilities, there have been modifications and improvements to enhance production and metal recovery, and to reduce the potential for discharges to the environment.

CSC is continuing to implement a voluntary program of systems upgrades to reduce the potential for discharges to the environment. Many of these systems involve primary controls with redundant secondary controls. This is not a new concept in the protection of the environment, what CSC has done is to expand the scale of the concept. Rather than having system components within inches of each other as you would in the hypothetical double-lined basin, CSC systems utilize site specific geologic characteristics coupled with engineered controls to create a group of facilities that act together to form a control system. It is this system concept that constitutes BADCT compliance at the CSC site.

When you look at a new facility BADCT design, what is being presented is a group of controls that make up a system. Take as an example, a typical double-lined basin where all of the

DAMES & MOORE

Arizona Department of Environmental Quality

February 8, 1995

Page 4

operating solutions are completely controlled. There is typically a leachate collection facility, and an impoundment with a primary liner, a leak detection system, a secondary liner, and possibly a secondary leak detection system. The system described above is accepted on an industry-wide basis as BADCT.

This hypothetical double-lined basin can be compared to the systems that CSC has built, with the primary difference being a scale change. The leachate collection facility could be compared to CSC's primary cutoff trench; they serve the same function. The primary liner in the theoretical double-lined impoundment and the primary pond liner are the same in both cases, and are typically constructed of the same material. The leak detection system in the double-lined impoundment is analogous to the secondary cutoff trenches, where any solution that passes the primary liner is detected and controlled. The next level of protection is the secondary liner in the theoretical double-lined impoundment; this can be compared to the downstream lined basin within the CSC system. The final control or verification would be the secondary leak detection device; within the CSC systems, this is the down gradient monitor wells, which also serve as the point of compliance.

This system philosophy is applied in many areas across the CSC property. An individual facility may not conform to a hypothetical optimal BADCT. The leachate collection or leak detection system in the theoretical example would not constitute BADCT if it were evaluated separately from the rest of the system. CSC is implementing appropriate and practicable technology for the minimization or reduction of potential discharges at each facility, with the intent that each of the facilities system philosophy is applied in many areas across the CSC property. An individual facility may is part of a larger system. The system should be used to demonstrate compliance to BADCT for existing mining operations and not the individual pieces of the system.

Each discharge control system at the CSC site will have a defined point of compliance. The point of compliance for each system will be used to verify compliance with BADCT regulatory requirements contained in A.R.S. 49-243.B.2. In response to the statutory requirements contained in A.R.S. 49-243.B.l (b), a technical and economic evaluation will be provided to ADEQ. This evaluation will provide a comparison of existing and planned facility upgrades to a maximum practicable facility upgrade. These relative comparisons of the system components or facilities will address the economic impacts, operational and technical feasibility, and relative discharge reduction achievable.

During the December 19, 1994 site visit, CSC indicated that a February 15, 1995 submittal date appeared possible for a response to the ADEQ completeness review. In preparing this letter, we

DAMES & MOORE

Arizona Department of Environmental Quality

February 8, 1995

Page 5

now realize that additional time is required to complete the response. CSC, therefore, requests a three-week time extension, to March 8, 1995, for the response to the ADEQ completeness review.