Norman Mulvenon - Is this rainfall unusual, or is it going to become the norm? I assume you’ve asked the National Weather Service.

If we thought “no-action” was a reasonable, justifiable course, we probably would have analyzed the National Weather Service trends in rainfall a bit further to see if there are predicted long-term climactic changes to make us less certain that “no-action” was a good approach. However, even if we could expect every year’s rainfall to be 50 inches dead-on, it wouldn’t solve our problem with enough certainty that we want to move forward with that.

Mr. Mulvenon - In the public meetings we had prior to the Proposed Plan and Record of Decision, several geologists said that the NT-4 stream could not be moved. This is “I told you so.”

There’s some truth to that. If we look at the groundwater situation as it exists now, we actually see some impacts of NT-4 continuing to drain, whether it’s the fracture patterns that are still in the bedrock, or some of the fill material was somewhat more permeable.

Ben Adams – You talk about the core team; I want to know who the players are… who’s designing it, who’s making the recommendations? Who is the risk taker? Who is paying for all of this (cost for redesign, study)? Anybody other than just us?

At this point we (DOE) are paying that out of our normal appropriated funds. In due diligence we are going back and examining details of the design and construction process to better understand the decisions, and if it’s appropriate, we may go back to the designer and analyze how this unfolded. There could be some costs recovered from the contractor, but it would be premature to speculate.

Mr. Adams –Could you have put anything in NT-4 like a 25-square-foot box culvert running the whole way and left the groundwater in it?

I’m not a soils engineer so I’m a little bit out of the area of my expertise, but I’m told that the best approach is the various sizes of aggregates simply for the long-term reliability. Even if you used concrete-type culvert, you might have questions about its long-term integrity.

Charles Washington – Given the interaction of materials inside the cell, what is the long-term reliability of the liner?

In terms of modeling that anticipates when contaminants would leave and where they would migrate to, they built in the assumption that the liner will cease to exist after 100 years.

Mr. Washington – What kind of material is it?

60 mil synthetic plastic.

Mr. Washington – From the time the liner is made, it begins to deteriorate. The manufacturer should be able to say how it will degrade. Once you lose the liner… we’ve got some pretty ferocious materials, and if they get out into the environment, they’re going to be a danger to all of the life in the immediate area.

We do have two layers; the top one and the second one and then we’ve got three feet of clay. It was designed to the most rigorous standards.

Pat Hill – No studies have been made with regard to global warming and rainfall patterns. We get a greater amount of rainfall as it is – was this taken into effect, given that 55 inches is probably a good, round number. This may be the way the world is changing now, do you see this design being functional if these facts are true, and was there a study done?

We stopped trying to analyze the prospect of more rain. If we were attempting the “no action” option and viewed this as an anomaly, it would be appropriate for us to have studied that. I don’t know if we have run models of what happens with 75 or 100 inches of rain with the types of remedies on the table, particularly the underdrain. I think the drain approach would accommodate higher rainfall if that turned out to be the pattern.

Ms. Hill - What happens to the water that has been pumped off and will it be monitored for contaminants?

We don’t really have water running out at the surface. We’ve measured it at wells and have had some damp spots. It’s not an issue really at the surface, but with the present cells having their “feet” wet. Ideally, you’d like to keep those and future cells dry.

Bob McLeod - How was the design long-term water table determined? Deterministically or statistically or both? Do you have a new design long-term water table?

With regard to the historical question, I think they were very aware that groundwater, depending on the particular location they picked, was going to be an issue. There were three contractors who submitted a 30 percent design of how they would build the cell. The contractor that was selected, Duratec Federal Services, actually moved the cell to gain benefits over the groundwater table which everyone knew was shallow, and to minimize fill requirements. They envisioned they would still have a 10-foot buffer. Clearly, something in the math didn’t quite work out.

Mr. McLeod – Couldn’t you go back to the U.S. Geological Service and look at long-term water level fluctuations and look at what the long-term recurrence intervals would be.

There has been a fair amount of study in the whole Bear Creek Valley system, with many monitoring wells in place to let us track and trend seasonal variations and correlate with annual precipitation. The models have been improved. In terms of how we can avoid this problem in the future, we’re in a much better position with a much more detailed model and more well control around the site. We have the benefits of studying this phenomenon with a lot more data.

Kerry Trammell – Do you know if incursions have caused any damage to clay liners that will need repair?

There are some limited areas where we appear to have water against the clay, which is very low permeability. The concept of the clay layer being the most important barrier for the cell just means that water won’t move quickly though it. The water table pushing up against the clay for a few months or even a few years like that shouldn’t cause any integrity concerns.

Mr. Trammell - Do we know that there’s not any undue pressure against that layer?

To the best of my knowledge, we do not have a concern with that.

Mr. Trammell – How much leachate comes off the cells, how is it handled and where does it go?

500,000 gallons of leachate have been collected through the leachate collection layer, the one foot of river rock. There’s a system of piping that transfers that from that rock layer under the southern berm where there’s a lift station that it collects and is pumped to five above-ground tanks.

Mr. Trammell – Can the tanks handle that, even with additional rainfall?

Yes. We haven’t had a problem trucking that to ORNL. As we fill up Cell 1, you tend to have less and less filtration. If we run a 12-hour shift, we can move 50,000 to 60,000 gallons a day to ORNL.

Mr. Trammell – When we look at modeling and the initial design of the cell, you can look historically at other cells that have been built; they don’t come close to having the groundwater issues we have. As far as modeling this is sort of a new. How reliable is information based on initial design of the cell and should that cause concern with the difference in information.

We have the benefit not only of better computers now, but we have excellent well control in and around present and future areas of the cell and we had the benefit of none of that information when the initial modeling was done. We were relying on general measurements in Bear Creek Valley itself and had to use a more rudimentary model.

Heather Cothron - When cells are all completed and the whole facility is closed, how much leachate do you anticipate on a daily-weekly-monthly basis, and how will that be disposed of?

Most of the leachate we’re getting right now is the direct result of rainfall entering the cell. When we completely finish, we’re anticipating .4 (less than one-half of one inch) of moisture will penetrate through the soil cap layers (the geomembrane, the clay) into the waste itself. Once that waste is completely drained and capped, you cut off rainfall. The most you’re going to get out is a half an inch a year long term.

Once the cell is closed and the cap has been in place for five to eight years, the leachate will drop to a very small amount. It drops from a very high rate just before the cell is closed and drops off very fast after closure.

Ms. Cothron – Your dates show you’re going to try to implement this in the summer of ’03, and I would assume this wasn’t anticipated as a cost. What work will not get done because this will get done?

Dave Adler - You’re right that it was not planned and we do have to round up the money. Our challenge is to do the most we can with available budget we have each year. Overruns have to be offset by under runs or project slowdowns, but there are no specific projects on the block because of this.

Ms. Cothron – What do the state and EPA feel is the best option?

John Owsley, TDEC - The state did participate in the selection and review of design of this facility from the start and we understood the questions that were posed by placing the waste cell in Bear Creek Valley, but as John Michael pointed out, that was a site selected for a number of reasons and the contingency plans that were built into the design and environmental monitoring plan attest to the concerns that were there. The state’s position is that we’ve accepted on-site disposal of CERCLA waste, with that given, we expect that this facility is compliant with all existing radioactive, hazardous and PCB or TSCA disposal regulations. All the options proposed would be compliant with those. We expect this facility to be safe and effective in the long term. We want to make sure that the public is well aware of the concerns and the options and has an opportunity to put forth their voice, concerns and recommendations on what options are selected. From the state’s perspective, the options will be compliant.

Connie Jones, EPA – This waste cell was built as a CERCLA waste cell and as such, EPA, in addition to the state, in response to our oversight responsibilities will ensure this waste cell meets the intended purpose. This waste cell will be subject to a five-year review.

Mr. McLeod – What groundwater model was used initially? What type are you currently using? What sensitivity analysis have you done?

Marshall Davenport - We used HELP, which is the Hydrogeologic Evaluation for Landfill Performance to model what was coming out of the landfill. We used MT3D which would model from there to the water table and we used an EPA model which was developed by Rogers & Assoc. to model from the water table to the hypothetical receptor. We are still using updated versions of those models. We’re using site specific detail now. We are in the process of doing the sensitivity analyses, specifically with the underdrain, looking at the conservatism of how to over design that, so that if efficiency were lowered, it would still move the amount of water we need moved. We have 10-12 peziometers we are monitoring weekly so we have a pretty good grasp on exactly what the groundwater in the immediate area is doing.

Chuck Agle – It seems as you build out the entire cells, the compaction would affect water flow under the cells, so when you put the drainage channel in, that would seem to be the preferred path. What would you anticipate the capacity of the drain channel to be? How long do you think it would take water to flow from the north end of the channel to the southern end?

In general the cut and fill there under the limestone and shale bed that underlies the cell, fracture systems seem to predominate in the groundwater flow. The fill we would put in lower lying areas wouldn’t impact the ability of the undisturbed layers to transmit water. The channel itself would be about 5,000 cubic yards of some good-sized aggregate river rock, more granite as opposed to limestone. We would expect about 7 gallons per minute to flow out of that. From north of the cell, we would actually continue to route all of the surface runoff that comes down Pine Ridge. As far as the time period, I’d estimate only a matter of minutes to hours to flow that distance.

Susan Gawarecki, LOC -

With the underdrain you’re obviously going to have to cut through the existing sub-liner system. Does that introduce weaknesses and how will you deal with that?

Actually, we have the benefit now – a window of opportunity – that if we choose this approach we’d be able to go in and put in the drain in the Cell 3 area without disturbing any of the liner that is already in place in Cells 1 and 2.

Ms. Gawarecki – It’s fairly ambitious to say you want to get it done this summer. Are you going to put it out for bid or extend current contracts of current contractors? How will time needed impact the overall schedule for needed cells which is already tight and may impact cleanup schedules?

If we reach consensus in the next several weeks, then it’s not our intent to bundle this with DFS who’s doing operations, or with the future contractor who’d be doing that build-out. We would do a separate contracting action. Bechtel Jacobs has fashioned an approach where they have a number of prequalified companies in place for various types of work. This option is such a straightforward approach that we’d be able to use existing contracting mechanisms. If we went into the trench, you’d definitely need more of a specialty contractor. There are a smaller number of companies capable of performing that work. That would take us into the next construction season, which would collide with the build-out construction.