FURTHER COMMENTS

Wetland treatment concepts in EPA/A.D. LITTLE draft Engineering Evaluation/Cost Analysis (EE/CA) Report on the Elizabeth Mine

This report is intended to describe the discussions at a meeting on November 7, 2001 between myself, Richard Downer, Cindy Clark, and representatives of the State of Vermont, the EPA, the Corps, A.D. Little, and various other federal agencies and expert consultants (a total of 12 individuals) This group had been assembled by EPA/AD Little to take a final look at the problem and the proposed alternatives and to insure that all critical factors have been considered and included prior to publication of the final EE/CA in December. The group had spent the day visiting the Elizabeth Mine site, our meeting convened at 3:30 that afternoon and was in essence an open discussion of any remaining issues. The meeting adjourned at 6:00 PM.

Most of the visitor participants were concerned with the geotechnical aspects of construction and the capping alternatives, since these are Richard Downer's area they will not be discussed in this report. One of the consultants was Mr. Robert S. Hedin, who was there to consider the "passive" treatment system proposals. I had known Bob previously and have a great deal of respect for his expertise and his opinions. He is one of the earliest proponents of wetland treatment for acid mine drainage, and is President of his own firm in Pittsburgh, PA. After inspecting the site and reviewing the available preliminary data he believes that the seepage from TP 1-2, because it is relatively low in aluminum, has a "moderate" pH, and some alkalinity, would be amenable to treatment with a wetland (for final polishing) preceded by either an anoxic limestone drain (ALD) (which is briefly mentioned in the EE/CA draft report and is described in my first report of 10/03/01), or successive alkalinity producing systems (SAPs) (also described in the draft EE/CA report and my report of 10/03/01), or sulfate reducing bacteria systems (SRBs) as proposed by Mr Jim Gusek (another ADL consultant). The SRB concept was not included in the draft EE/CA report, but is described in my second report (10/15/01). The choice of the best option should depend on collection of further data and pre-design pilot testing. In Mr. Hedin's opinion the seepage from TP 3 presents a far more complex and difficult to treat problem; the seepage is highly acidic, and contains high concentrations of aluminum and iron. Under these conditions, neither the ALD or the SAP may be appropriate and maintenance requirements might be very high for the SRB, and continue for many , many years. The most positive approach to this critical problem would be to either remove the TP 3 tailings or cap them.

It is my assessment that Mr. Hedin's proposals, and opinions, rank somewhere between the draft EE/CA and the proposals by Jim Gusek (see my report of 10/15/01 for a description of these). I would agree that the seepage from TP1-2 can be adequately treated with either an ALD, or a SAP, or a SRB as the initial treatment unit. The final selection will depend on sizing requirements and on operation and maintenance costs. Sizing will only be possible after further data is collected and possibly pilot testing, so the EE/CA report should include information on all three concepts as potential alternatives. The operations and maintenance requirements are a critical issue since the State of Vermont must accept responsibility for these aspects. The wetland component, as used in the passive treatment system, have been in use for many decades and do not require frequent cleaning or similar maintenance. An ALD may require replacement of the limestone media every 50 years, The SAP is claimed to require media (compost & limestone) replacement every 12 to 15 years, and a flushing of the media every 6 to 8 months. The SRB, according to Jim Gusek, would require only media (cattle manure & limestone) replacement every 25 to 35 years. These media replacement estimates are theoretical estimates since none of these concepts have been in routine service for more than five or six years. This is an important issue for both the State of Vermont and the community residents since media replacement will require expenditures by the State and contract truck traffic for removal and replacement of the material. If TP 3 is maintained in it's present condition for historical reasons this maintenance requirement could persist for generations. If TP 1-2 are properly capped and seepage reduced to a minimum , the useful life of the treatment components could be extended and long term replacement maintenance possibly reduced to a reasonable period. Based on my experience with estimates of this type I believe the 25 to 35 years for the SRB and the 15 years for the SAP may both be too optimistic. I would suggest more conservative values be adopted for planning purposes, say 15 years for the SRB and 10 years for the SAP. Flushing, twice a year for the SAP would also be a conservative assumption at this point. It is unclear, at this point if similar flushing might be required for the SRB.

The draft EE/CA report only mentioned ALDs in passing, and clearly indicated that SAPs would be used to treat both TP 1-2 and TP 3 seepage. At the later meeting with Jim Gusek and EPA/ADL the impression was then clearly established that SRBs would be used instead of SAPs and my report of 10/15/01 described this change. However, as indicated by Mr Hedin at this most recent meeting it is premature with the limited data we now have available to make a final selection of the preferred technology. I concur in this opinion. As a result, the final EE/CA report will present all three alternatives for possible use at TP 1-2. However, the costs presented in the draft EE/CA report may not be changed. These are preliminary estimates, typically valid within 25% to 30% of the actual costs, and are believed conservative enough to cover any of the various alternatives, with two exceptions. The operation and maintenance costs are based on a once per year flushing of a SAP and a 15 year replacement cycle. These costs would increase if the more conservative schedules I recommended previously are adopted. The final selection of the treatment process components will occur in pre-design following analysis of additional data and possibly pilot testing.

Now that ALDs and SAPs are back in consideration, the concern I expressed in my report of 10/03/01 regarding winter ice formation on the wetland is also back in the picture. There has apparently been some confusion on this point. It is true that biological and some chemical reactions slow down during cold weather, but I am not concerned about that as an issue. You compensate for those problems, during design, by making the wetland larger for winter service. My concern relates to the formation of ice on the wetland. With the ALD and SAP concepts the iron is expected to oxidize and precipitate in an "aerobic" wetland. In most months of the year with an "open" water surface this will not be a problem and will happen automatically. In the coldest part of the winter however, there will be a continuous ice cover on the wetland, with the oxygen source from the atmosphere cut off the wetland will no longer be "aerobic" and may no longer remove the iron to a satisfactory degree. You can't solve this problem by making the wetland bigger, that results in the water getting colder and the ice getting even deeper. In a really cold winter, without a snow cover, we might get up to three feet of ice on ponds and wetlands. The seepage coming out of the tailings piles should be about 44°F during the winter months so ice formation on all exposed water surfaces can be expected every winter. Mr Hedin agreed that this aspect must be considered during predesign for the Elizabeth Mine. He indicated that systems in Pennsylvania have no problems with achieving water quality goals in the winter, but the climate there is milder and more variable than we experience here in Vermont. My concern on this issue is based on my personal experience, and that of others, with wetland systems in Canada.

Sherwood C. Reed, P.E.
Principal, E.E.C.

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