Review Comments: The EPA/ADL Presentation at CAG Meeting January 23, 2002

I was unable to attend the meeting, but I have reviewed the written material presented by EPA and have exchanged Emails with Ed Hathaway to request additional data and to clarify several issues. These data, consisting of detailed spreadsheets describing the development of the new O&M costs have been sent to me by ADL.

At the meeting, the EPA presented: (1) The reports by their experts who had reviewed the EE/CA report and actually visited the site in November 2000, (2) a "new" treatment sequence for TP3 if it is decided to preserve the entire site, or a portion of the site, and (3) revised costs for the entire project, these included a large and rather startling increase in operation and maintenance (O&M) costs for the TP3 treatment system.

The acronyms for the various treatment system components in this project are becoming somewhat confusing and the number seems to grow with each iteration. At the end of this report, I've made a list of the acronyms, and some of the other critical technical terms, in current use with a brief description of each.

(1) Expert's Review

These individuals included five internationally recognized consultants with significant experience in acid mine drainage (AMD) work, an expert from the U.S. Geological Survey, and an engineer from a company with experience in constructing and managing corrective action at AMD sites. All of these people have reviewed the draft EE/CA report and inspected the site. Their comments can be found in the report "Elizabeth Mine Engineering Evaluation/Cost Analysis Comments and Technical Review Reports," presented at the January 23rd CAG meeting. The two Technical Advisors to the CAG had previously reviewed the draft EE/CA report and also offered comments.

It is the consensus professional recommendation of all of these qualified reviewers that the tailings piles at TP3 should be removed completely. The reason behind this consensus opinion is the presence of the highly acidic seepage containing high concentrations of metals. This seepage will be very difficult and expensive to treat. However, because of the local interest, options were presented for retention of TP3 and treatment of the seepage. There was no consensus by the experts on the proposed treatment (ALD followed by a SAP followed by an aerobic wetland in the draft EE/CA report). The majority believed the proposed system would not perform as intended without excessive operational and maintenance attention and costs. I shared those concerns.

As a result of these concerns the EPA then tentatively proposed SRB's instead of SAP's. Concerns were then expressed because of the high iron and aluminum concentrations in the TP3 seepage. A significant amount of these metals might be separated within the SRB, this in turn would result in clogging of the bed resulting in failure and/or requiring very frequent maintenance. To overcome these problems, a third iteration of the TP3 treatment sequence has now been proposed, and will be described and discussed below.

The fact that we are in the third iteration of a possible treatment sequence should not be taken as a criticism of EPA or ADL. Such changes are normal in the development of most engineering designs and it should be remembered we are still in the conceptual stage on this project. However, the fact that we are now at the third iteration is strong evidence of the difficulty of treating the acidic TP3 seepage. As noted in my comments below, I still have reservations regarding the ability of this "new" system to perform reliably on a year-round basis here in Vermont. It is possible that the system which is finally selected could be even more complex and more expensive.

Acid mine drainage has been successfully treated at a large number of locations in the U.S., with some systems being operated for over 20 years. These, however, are mostly coal mining operations and do not contain the very high concentrations of the types of metals present in the TP3 seepage. The treatment sequence now proposed for TP3 has not been used at any other site, to my knowledge. Some of the components have been in successful use for three to six years (an exception is conventional aerobic wetlands, these have been used for many decades), but there is no experience with the long term period required at TP3. The revised projections to 100 and 200 years, instead of the typical 30 years used at most engineering projects, are valid. I cautioned in my first review of the draft EE/CA report that O&M would be required for "generations," apparently the EPA now concurs. The rock particles in the TP3 tailings piles have been exposed to the environment for many years already and the seepage is still highly contaminated. These rocks will not be "clean" in the near future, contaminated seepage will continue until the acidic tailings piles are almost completely dissolved, or completely covered, or removed.


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The "New" Treatment Process for TP3

This new treatment sequence has been developed to solve perceived problems with the earlier proposals. Both the SAP's and SRB's are in some ways similar to a filter bed. The water passes down through the media and biochemical transformations occur which then permit the settling and separation of metals in the unit or in subsequent components. In the case of TP3 seepage, the water has very high concentrations of aluminum and iron, and may also contain significant dissolved oxygen. These factors could allow the precipitation of aluminum and iron inside the SRB resulting in unacceptable clogging. The EPA consultants now believe it will be necessary to remove the iron and aluminum prior to the SRB, so we now have a SPAD (Semi Passive Alkalinity Doser), a mixing channel, and a settling pond ahead of the SRB unit. As the name implies the SPAD is semi-passive and uses a water wheel to drive the feed mechanism for adding an alkaline substance to the water. The increase in alkalinity allows the iron and aluminum precipitation reactions to begin; the mixing channel, probably lined with coarse rocks to induce turbulence, insures high oxygen levels in the water so the iron and aluminum can oxidize, precipitate, and settle out in the settling pond. This reduces the SRB clogging potential considerably, and the water then passes through the SRB for removal of copper, lead, zinc and cadmium. Effluent from the SRB then runs down an aeration channel to the wetland. The purpose of this rock lined aeration channel is to increase the oxygen content of the water before it enters the wetland. The final component is the aerobic wetlands. The wetlands are planned for BOD and manganese removal with a "combination of rock filters and algae mats." Details were not provided on the configuration of these features but it is indicated that manganese oxidation will occur by contact with algal mats of leptothrix discophora algae. In accordance with federal and Vermont standards the water at the end of the treatment system discharge pipe, prior to any mixing or dilution in a stream, would be the point of compliance measuring. The cost estimates provide an allowance for sampling and testing.

It is indicated that all of these components are in use at ADM sites elsewhere. For example, a list is given of 19 sites where the SRB unit is in use. Scanning the list indicates that 17 of these systems are pilot scale, or even smaller "bench" scale units. The one full scale application, at a mine in Missouri, designed for lead and zinc removal, has been in operation for up to 5 years. We have a much more severe winter climate than Missouri so extrapolations are not possible. A pilot test of the entire proposed treatment process at the Elizabeth Mine would be absolutely essential prior to final design.

I am still concerned about the impact of our winter conditions on the proposed system, both on performance and on the ability to function at all. The design cannot assume that Global Warming will convert our climate to the equivalent of Pennsylvania's or Missouri, if the system is expected to run continuously throughout the winter it must contend with worst case conditions. Based on 42 years of record at the Lebanon, NH airport, the coldest winter in the Upper Valley occurred in 1970, the average January temperature was 18°F, in February 21°F, and in March 31°F. The extreme temperature in January was - 28°F. Under these conditions, with three continuous months of sub-freezing weather, ice will certainly form on all of the ponds, on the wetlands, and on the mixing and aeration channels. The latter are most susceptible to icing and a long period of sub freezing weather could result in creation of an ice glacier and subsequent overflow from the channels. It is also unclear how the algae in the wetland can perform their intended function at expected winter temperatures and under an ice or snow cover on the wetland since either ice or snow cover on these wetlands will occur every winter, and the algae require exposure to sunlight to function. It is true that a deep snow pack will act as an insulating barrier and retard freezing. The ground in my front yard will remain unfrozen if we get an early snowfall in November and the snow persists and accumulates all winter. That, however, is not the typical case. We more often have a cold December and no snow until January. The most reasonable solution for TP3 treatment might be to design this system for seasonal operations, say from early April to late November, with the seepage being stored in the holding pond during the colder months.

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I also have concerns about the summer performance of the proposed wetland. It is not quite the same as the typical constructed cattail marsh used at many coal mine AMD sites. The wetland is to have rock cobbles on the bottom, presumably to provide the surfaces for the algae to attach and grow, and at least three species of plants will be planted. However, the algae require exposure to sunlight and if the plants grow and multiply they will shade the water surface, and without sunlight the algae will die. These aquatic plants also die back each fall, if the litter is not harvested, and removed, it may smother the algae. Apparently the algae mat for manganese removal is being proposed since the familiar cattail marsh is not too effective for removal of this metal. I have no personal experience with using algal mats, but am aware they have been demonstrated in Florida and California and achieved excellent removals of phosphorus and metals. Those systems incorporated frequent algae harvesting because if the algal cell is allowed to die and decompose there is a release of substances back into the water. Algae harvesting would not be feasible at Elizabeth Mine. Algae also require nutrients (ie: nitrogen, phosphorus, etc) to grow and function. Such nutrients are not normally present in the ADM waste flow, but may leak in sufficient quantities from the SRB component.

Another proposed wetland function is removal of BOD, because the SRB will leak organic material as BOD (Biochemical Oxygen Demand). The concentration may be significant for three to six months and stabilize at 10 mg/L according to the EPA handouts. A 10 mg/L BOD concentration is already below typical discharge standards in Vermont so it is unclear why the wetland is needed for this purpose. In my experience, a wetland system will discharge from 6 to 8 mg/L BOD as a "background" level due to the decomposition of natural organic materials present in the wetland.

The title "Aerobic Wetland" may also be a misnomer. The term "aerobic" implies the presence of oxygen. It has been my experience, that in constructed wetlands with water depths of one foot or more, only the water very near the surface has any oxygen, the bulk of the water in the wetland is essentially devoid of oxygen (or "anoxic"). If the water depth is limited to a few inches the entire depth may be "aerobic." In the winter time, after ice forms, even the surface layer of water in the deeper wetland is essentially devoid of oxygen, except near the front end where the water enters. The "new" treatment sequence proposes the use of an aeration channel ahead of the wetland in order to increase the dissolved oxygen in the water entering the wetland. It has been my experience, with wetland systems elsewhere that such oxygen will be rapidly utilized near the front end of the wetland and will not contribute to aerobic conditions in the remainder of the wetland.

In summary, I still have reservations about the ability of the "new" TP3 treatment system to provide all of the intended treatment responses and to even function effectively in the Vermont winter. I believe the most prudent choice may be to completely remove the tailings piles at TP3. However, if it is decided to preserve all or part of TP3 I also believe a functional treatment system can be developed after pilot testing. Such a system will be very complex and very expensive to operate as evidenced by the increasing cost estimates presented so far by the EPA.

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Cost Estimates

The most recent cost estimates for operation and maintenance of a TP3 treatment system have risen dramatically. Sufficient details were not given at the January 23rd presentation so it seemed desirable to review the estimating data and procedures carefully to be absolutely sure the numbers were valid. I asked the EPA for such data and it was immediately provided by ADL. It consists of a massive (>5000K) multi paged spread sheet. This spread sheet contains a preliminary sizing of the various treatment components, made by the consultant engineers, estimates of the materials and labor and costs required for construction and estimates of costs for operation and maintenance (O&M). A one page summary of O&M costs was also provided and a hard copy of this is now on file at the Copperas Hill Coalition (Kathy Hardy). I have reviewed all of these these data and conclude that the projected costs are valid and realistic and were developed using standard procedures. It must also be remembered that we are still in the conceptual design stage and any cost estimate at this point is at best valid to within about 20 percent of the real costs. It is likely that as we get closer to the final design these costs will continue to change and are likely to get even higher. As an example of the estimating procedure I have presented below more detailed values from the ADL spread sheet to demonstrate where one of the summary costs presented by EPA came from.. The O & M (called PRSC costs by EPA & ADL) include two major components, the actual annual costs that occur every year and recurring costs that occur on a less frequent schedule. In the latter category, for example, would be replacement of the media in the SRB. A more realistic replacement schedule of 10 years has now been adopted in the ADL estimate. The original, somewhat optimistic schedules ranged from 15 to 25 years, but there was no actual experience to back up those estimates. I objected to that in my original review and believe the 10 year cycle is more realistic. Another major change from the draft EE/CA report is the assumed life cycle cost period. As with most conventional engineering designs the draft report assumed a 30 year period. In my review at the time, I indicated the O&M costs would continue for generations. EPA now agrees and has assumed a period of at least 100 years for costing purposes. This means that the recurring costs will be repeated 10 times over the 100 year period instead of just once with the 30 year assumption.

The actual estimated annual costs, assuming a non-hazardous sludge, for TP3, include:

The recurring costs occur on a ten year cycle, the present worth of these costs is determined and then distributed as an equivalent annual amount. These annualized amounts are:

When you add these two sets of costs, the total is $254,330 which is the same as the summary value for the complete preservation of TP3 with a non-hazardous sludge, presented by EPA at the November CAG meeting. The annual O&M costs for a hazardous sludge were $400,000. At this stage, I think it would be conservative and prudent to assume that the sludge requiring disposal would be hazardous. Hopefully, information would come from a pilot test to define sludge characteristics.

In summary, I believe these cost estimates are reliable for this stage of conceptual planning, and were derived using appropriate methods.

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

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GLOSSARY

AEROBIC WETLAND
A constructed marsh with growing plants. For most coal mine systems this is often a simple cattail marsh. For TP3 a rock substrate to support algae, and plants are proposed. These wetlands are used for final polishing of the water. Some kind of wetland is a likely component for both TP1/TP2 and TP3.

ALD
Anoxic Limestone Drain. A deep trench, filled with limestone. The trench is covered with a clay cap to prevent the entrance of oxygen, hence the term "anoxic." seepage enters through one wall of the trench and passes out the other. During the time the water is in the trench it acquires alkalinity from the dissolving limestone. This alkalinity permits metal precipitation at a later stage. An ALD may be used in the treatment sequence for TP1/TP2.

ALKALINITY
An alkaline water contains carbonates or hydroxides, highly alkaline waters are called "hard" and can precipitate deposits on your teapots and cooking vessels. Water softeners are used to remove this alkalinity from hard waters. Acidic mine waters tend to have very little alkalinity and this prevents the precipitation reactions that allow metals removal. It is typically necessary to add alkalinity to such waters to allow treatment.

BOD
Biochemical Oxygen Demand. A laboratory test of water quality. An indicator of the amount of degradable organic material in the water.

LEPTOTHRIX DISCOPHORA ALGAE
A species of algae which attaches to surfaces on the bottom of streams. Has been shown to be very effective for removal of some metals. Requires sunlight, and nutrients to live and function.

SAP
Successive Alkalinity Producing system. A shallow pond containing a layer of limestone on the bottom overlain by a layer of compost, with underdrain pipes located in the limestone layer. The mine water passes down through these layers where biochemical reactions increase the alkalinity and prepare conditions for precipitation of metals in the next treatment unit (typically the wetland). The underdrain pipes alos are used to flush the bed periodically. The SAP is a possible treatment concept for TP1/TP2.

SPAD
Semi Passive Alkalinity Doser. This is a tank containing limestone chips or pebbles, or some other alkaline chemical. An attached water wheel drives the feed mechanism so the does of chemical is compatible with the amount of water flowing by. The purpose is to provide sufficient alkalinity to permit the removal of iron and aluminum in a settling pond. A possible treatment unit for TP3.

SRB
Sulfate Reducing Bacteria bioreactors. The SRB is similar to the SAP in that water flows downward through the media. But in this case the media largely consists of high strength organic material, such as raw cattle manure which contains sulfates. The bed is devoid of oxygen and the biochemical reactions produce metal sulfides which then settle out. Wood chips, alfalfa hay, and other organic materials have also been used. Limestone gravel is usually included in the mixture to improve permeability and provide a supplemental source of alkalinity. The SRB is susceptible to plugging if high concentrations of iron or aluminum are present in the water. An SRB is now proposed for TP3, after the iron and aluminum have been removed.

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